# Toyota Check Engine Light on and Error Code is P0171 - What needs to be fixed? - Finally Fixed see p



## Don2222

Hello

I have a 1999 V6 Toyota Solara and trying to fix the Check Engine Light

The Auto Zone Code Checker says the following:
Troubleshooting P0171
OEM Brand: Toyota 
Definition 
Air/Fuel Mixture system lean bank 1 
(Cylinder Number 1 denotes bank 1) 
Probable cause 
#1.- Low fuel pressure
#2 - Faulty "MAF/VAF sensor"
#3.- Cylinder misfire condition
#4 - Faulty H02S/AF sensor
#5 - Large Vacuum leak 

First I replaced the downstream O2 sensor and both upstream O2 sensors but that did not help.
  The exhaust was leaking so, I had the front flex pipe before the catalytic converter replaced which was before the down stream O2 sensor. That helped and no light when driving around town for a couple for days, but the check engine light came back on when driving early on a cold morning on the highway.

The Toyota parts man said their front flex pipe is part of the catalytic converter and is an over $2k install. My mechanic is really a super guy, he installed just the flex pipe for $150 !!
The Toyota parts man also said that if the exhaust was a problem with the check engine light then there should be an additional 420 error code and in my case there was no 420 error code!!

Nice vid on MAF - Mass Air Flow Sensor
http://www.youtube.com/watch?v=sSuL58YEH-E

*The Answer appears to be:

If it is not a vacuum leak then the MAF - Mass Air Flow Sensor or A/F Air/Fuel Sensor if there is a P1135 error code also!

I also found this from  http://www.toyotaownersclub.com/for...4e90d4c548e9b947301feb65&showtopic=9206&st=15
Posted 11 August 2004 - 12:25 AM
I can almost guarantee you that your PO171 code is because of a bad Mass Air Flow Sensor (MAF). I work at a Toyota dealership and we see this problem alot and 99 times out of 100 it is a bad MAF. Hope this helps. 

Posted 14 October 2004 - 12:24 AM - This refers the the Air/Fuel A/F sensor not the Mass Air Flow (MAF) sensor 
This A/F sensor and computer problem is widespread. Toyota probably does not want to admit it. There probably is a malfuction in the match up between the computer and the sensor (feedback loop) that is preventing the air and fuel ratio to be mixed properly. I would also venture to speculate that this problem involves other Toyota products other than Camry, that use this same subsystem for fuel delivery.

I have to say that the dealership where I take my car was very fair and replaced both the A/F sensor and computer. It turns out that the 97 Camrys have an old version computer that is related to the problem. When I spoke with the master mechanic he told me that after taling with the factory, Toyota's recommended fix was to replace both the sensor and computer (over a $1000 in parts alone). Much appreciated was that he got the parts to be covered by Toyota and I just had to pay for the labor only. When this problem first occured I was under 100k but am now at 104k. This was the third time I had brought the car in and had already spent over $300 in labor.

While I was waiting in line again the service person at the front desk was on the phone describing to the customer that they had a check engine light on with a lean condition, and that they were going to try to clean the A/F sensor........"Yes maam.... that would account for the split second hesitation in power..........

The master mechanic said that one of the other mechanics had my same car (97 Camry) and he too had the exact same problem - hesitation in power, followed by check engine light, followed by lean condition codes. Also said that replacement of the computer and sensor resolved the check engine light from coming on but he still gets that split second hesitation in power.

Notes from the service write up: Code P0171 (system too lean) code P1135 (A/F Sensor heater circuit malfunction bank 1, sensor 1). Tech tested A/F sensor on scan tool and sensor is not responding to lean command. Tech prelaced ECU and A/F sensor.

Hope this information helps. This might end up in the news at some point as a product recall due to defective design. *
  I do not see any vacuum leaks so I am getting a new MAF tomorrow.

*Did anyone have the same error code and know what caused it?*


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## nate379

MAF sensor problem should also give you a P0174 code, lean on bank 2.


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## Don2222

NATE379 said:
			
		

> MAF sensor problem should also give you a P0174 code, lean on bank 2.



Hi Nate
Interesting, you said that because the P0171 code was all I got from the Auto Zone free check. However when I got desperate because it is close to inspection time, I paid the $94.00 for the Toyota Data check. Here is what they found:
P0171 - Fuel Trim
P0100 - Air Flow Meter
P0110 - Air Flow Malfunction

What makes me angry is that I paid about $75 dollars last year at AutoZone for a new MAF and it did not do anything but throw me down the wrong path of what to fix!
I could have done better at a Junk Yard!!

Toyota says you must buy our $231.90 part or it May Not work!! So I bought it and installed. Let's see what happens!!

Below are the pics of the Auto Zone MAF and the Toyota MAF and I see no difference, even the labs say Toyota!
The last pic is the Old Auto Zone MAF the others are the new Toyota MAF


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## nate379

I'm just thinking why would bank 1 show lean and not bank 2 if the MAF is not working?  The air going through the MAF is going to both banks.

I'm not a Toyota tech or even drive one, last one I owned was a 72 FJ40, but that is just my thought on it.


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## kettensÃ¤ge

Blocked injector?
I would think the system would pick up a misfire and display that code as well.


Never mind I see you may have gotten it fixed.


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## kettensÃ¤ge

http://www.solaraguy.com/viewtopic.php?f=1&t=24992

Just in case.


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## Don2222

Hello

Thanks, you guys. After replacing the AutoZone MAF with the OEM Toyota MAF Mass Air Flow Sensor or Meter as they call it, the car runs like a top! Much more pickup and the Check Engine Light is Finally OFF!!

Hope this helps others! Thanks again for your comments. Maybe I will add some fuel injection cleaner also.....


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## CTburning

I work as a service advisor for Lexus and see it all the time.  When I worked for Nissan it was even more so, Don't buy aftermarket electrical parts/sensors for the Jap cars!  o2 sensors, maf's, etc are precision monitoring devices and while you might get away with it some of the time, the most expensive job is the one you do twice.  If you need struts or a tie rod, call autozone.


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## Don2222

CTburning said:
			
		

> I work as a service advisor for Lexus and see it all the time.  When I worked for Nissan it was even more so, Don't buy aftermarket electrical parts/sensors for the Jap cars!  o2 sensors, maf's, etc are precision monitoring devices and while you might get away with it some of the time, the most expensive job is the one you do twice.  If you need struts or a tie rod, call autozone.



Hi DTburning

*Can you explain why AutoZone has the same Toyota Denso Tag on their part? *

  I heard from a very experienced semiconductor industry executive who is a leading expert in failure analysis, that there is an enormous market in Japan for what is now called "Counterfeit Electronic Parts". Japan has been buying our old electronics for many years and removing the parts. These parts are sometimes tested, sometimes reconditioned, and sold for a very high profit! Electronics that are made with these older parts my have bad tolerances, and many times a very high failure rate! They now have tests that can tell if these parts are not new, and that is why places like AutoZone can charge alot less!!


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## gpcollen1

wish I had seen this earlier.  Chances are that you replaced that part for NOTHING.  Most of the time, all you have to do is clean the MAF.  Take it out and spray it with electrical parts cleaner.  Some do it multiple times, some use a Q-tip to actually clean it.  Bottom line is that it gets dirty...and is a well known issue.  I cleaned mine at about 85k and it cleared the code.  Now at 200k and nothing yet...


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## Don2222

CTwoodburner said:
			
		

> wish I had seen this earlier.  Chances are that you replaced that part for NOTHING.  Most of the time, all you have to do is clean the MAF.  Take it out and spray it with electrical parts cleaner.  Some do it multiple times, some use a Q-tip to actually clean it.  Bottom line is that it gets dirty...and is a well known issue.  I cleaned mine at about 85k and it cleared the code.  Now at 200k and nothing yet...



Hello CTwoodburner

Thanks anyway. I am glad that worked for you because it did not work for me. Even though the two metal sensing posts did not look dirty, I tried cleaning them with a Q-Tip and MAF cleaner, I purchased from AutoZone. See pic. Then I reset the code by removing the Positive Battery Terminal for over 1 minute and it came back on again after driving it for a day or so!

So it has been almost a week now with the new OEM Toyota MAF and still NO Check Engine Light! I think I am all set.

What kind of car do you have? Do you have the same MAF as in my pic in the earlier Post?


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## mayhem

Sounds like you bought a bad MAF from Autozone...either it was bad in the box or you touched the wires when you installed it.  If it was a recent purchase you cna try to return it as bad out of the box, but I bet its been too long and you have to eat it.

I've never heard of using qtips to clean the MAF...everything I've ever heard or read says use the MAF spray only, never touch the wires with anything or you'll soon be looking for a MAF.


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## Don2222

Hello

Sorry to say the Engine Check Light came back on today as I stopped at a Red Light. (The braking here had something to do with it but I did not know at this time!!) I reset it and the check light came on a day later as I was driving down the main st in town and braking again! Took it back to AutoZone for a check and guess what? P0171 code is back    :-(

So I dumped in a bottle of Fuel Injector Cleaner and started ripping out and replacing the vacuum lines. I got 5/32 rubber vacuum lines at Pep Boys in which the ID is very close to the small metric lines but the thickness of the Pep Boys lines are greater.

So I just did most of the lines under that Engine Cover Plate by taking the plate off with a Torx socket set.

Someone said they fixed the P0171 code by replacing the vacuum hoses to the canister under the battery. I have to get the Toyota hose for that since the added thickness on the American hose will make the hose not fit into the engine clamps and if the hose touches the engine it could melt. Oh well hope it helps!!


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## moosetrek

My MAF story...  I bought a 91 Nissan Pathfinder for cheap because the oil pump was shot (basically required removal of the engine to get to it).  Many cuss words later, and after replacing the timing belt twice, running compression tests, and replacing plugs, wires, etc. it still belched black smoke and wouldn't idle.  I was so convinced that either timing was off (set it three times) or the upper end was shot from the blown oil pump I almost gave it away in frustration.  I tried one last thing, and looked up the codes.  It showed a bad MAF.  Cleaned everything, checked all the connections, and finally I looked and one of the wires to the MAF had been pinched in a nut.  A 5-cent wire nut and it ran like a kitten after a laser pointer; no smoke, idled perfect.  I learned that sometimes it's possible to overanalyze modern cars.


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## kettensÃ¤ge

Some of my experiences:
Wife's Subaru continually running worse and worse, lack of usual power, hesistation, etc. No engine light. Car refuses to run one day, wife gets stuck. I got it home driving with 2 feet. Put the scanner on it, MAF codes come up. Replace it with a rebuilt MAF from AutoZone. Not much better but at least it ran without stalling. Scanned it once again and find 02 readings not quite where they should be. Replace the front 02 sensor, bingo!! There was no engine light until the day she got stuck. The rebuilt by Cardone MAF is working fine, less than 1/2 the cost of new at Autozone, Didn't even call the dealer. This was a Subaru part that they dissasembled, repaired and sold. 

Most automotive components are made by companies and sold to car manufacturers or the after market. Car companies don't build parts like these, they buy them. I have bought some Duralast, Wells, Airtex, and Standard brand parts that were Identical to factory installed parts, right down to mold numbers and date codes. Think of the cost to duplicate a MAF sensor or other complex electrical part and then hope to sell enough to make a profit, and gaurantee that it will be problem free and work equal to or better than O.E. Parts stores don't manufacture parts like these, they buy them from the same suppliers that car companies do. The engineering is done by the car company and given to a parts supplier to build. Do you think Toyota has a plant somewhere building MAF sensors for 12 year old cars? I take a chance on aftermarket parts with good results so far.

Some parts are different, and some are dealer only.

I also search the net for others that are having the same problem. If you find consensus to solve a problem that you are having on a few different websites, most likely it will work for you also. The effort is already put to the problem by someone else, you just have to find their solution and duplicate it.


I found the link in my post above by searching "99 solara v6 p0171" 
Message boards like this one that pertain to a certain brand or model of car are invaluable sources of information, just think car instead of "hearth".


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## Don2222

Hello

Thanks for your stories Moosetrek and kettensÃ¤ge. I appreciate the information. 

  My saga continues and I may have really nailed it down this time. Well when it came back on again the other day, I ripped off the engine top cover and started replacing vacuum lines. The small ones I could replace with the Pep Boys 5/32 line. When it came time to run new lines from the vacuum reserve canister under the battery, those PepBoy auto part store American lines were too thick to slip into the engine clips to hold them away from the hot radiator hose and hot engine. So I went to Toyota dealer and found all their hoses have part numbers even though they were the same size! One of the $12.00 hoses to the vacuum reserve tank was not made anymore! Then the parts guy found 6 feet of 5/32 hose with a smaller OD so he just gave it to me. So I replaced the canister lines but the 12 year old lines being a little stretched and stiff still seamed to make a tight seal so I was disappointed. I went back to Toyota and talked to another parts guy and told him about the P0171 code and what I replaced. He asked another tech that I never got advice from before. He suggested a bad vacuum booster behind the master cylinder and the brake pedal being harder to press. Well the brakes seamed not quite as good the last year! So I came home, and thought the booster itself never really goes bad but there were some larger vacuum lines connected to it. The main line from the booster to the engine was loose as a goose at the engine! Then I realized how the last 2 times the check engine light came back on after I reset it was once at a stop light and once when I was breaking in traffic Bingo, Ding Ding Ding
So instead of buying the preformed vacuum hose at Toyota that uses those squeeze clamps for $30.00, I went to the auto store and got 3/8 vacuum hose and radiator clamps $5.00 Total for a nice tight seal. After 10 mins it was all done and wow the brakes do work better!

So I think I am all set now!! See pics and I will know for sure in a week or so !! Sigh of Relief!!

Yellow arrow shows leaky end in 1st pic and fixed end in 2nd pic! Third pic shows the rest of the new hose up to the Vacuum Booster


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## smoke show

whenever your getting a lean code the first thing to check is for vacuum leaks thoroughly.


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## Don2222

smoke show said:
			
		

> whenever your getting a lean code the first thing to check is for vacuum leaks thoroughly.



Hello smoke show

  Yes that is true and of course Hind Sight is 20/20. I did check the vacuum hoses on the engine especially the two that go to the vacuum reserve canister under the battery and they were tight! Also after replacing the AutoZone re-manufactured MAF it was good for almost a week! I am thinking now that this was not an entirely static problem! The new OEM MAF gave the car more Zip and I probably used the brakes more which exaserbated the vacuum booster hose leak at the engine. This vacuum leak at the engine is also effects vacuum in all the other places just hard to think of at the time!!

I did not see that vacuum booster hose as a problem anywhere else on the internet so I wanted to document it here and now we all know!!

So thanks every one for your comments and stories to help nail this problem down and help more people who see this in the future


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## Don2222

Hello

Well the Eng Check light is back on!! This is so frustrating!! Toyota says change the Vacuum Booster behind the Master Brake Cylinder!

Here is some good diagnostics
From
http://www.2carpros.com/articles/repair-lean-mixture-codes-p0171-or-p0174-on-some-manufacturers
Repair Lean Mixture Codes (P0171 or P0174 on some manufacturers)

  The engine management system is designed to control the air fuel mixture the engine consumes. This system controls the air fuel mixture according to sensor feedback data. There are two types of lean mixture conditions, computer controlled and non-computer controlled malfunctions. Also, there is a different diagnosis if there is lean mixture codes for one side or the other of the exhaust system, bank 1 or bank 2 (V10 V8 V6 only) and a lean codes for both sides of the exhaust system. If there is a lean mixture code for one bank or the other it typically means an engine cylinder or injector is having a problem. On this page there are two sections; Section 1 is for lean bank 1 or bank 2. Section 2 is for lean system codes (lean on both sides, bank 1 and 2). Common misconception: When an engine miss-fires it creates a lean condition not a rich one and this is why all engines run on an optimum fuel to air mixture called "stoichiometric" which means chemically balanced. This balanced fuel to air ratio is 14.7 to 1, 14.7 parts air to 1 part fuel. When the engine misfires it releases more air (14.7 times more) then fuel, creating a lean mixture. When a lean mixture code is present you must consider how the engine is running before diagnosis begins. We have listed the most common reasons for a lean mixture code below:

Car Repair Guide - READ COMPLETELY!

Section 1 - Lean mixture code for bank 1 or bank 2 (V6,V8,V10 and V12 engine only)
    *
      Step 1: Use a simple scanner tool to retrieve trouble codes and check if they relate to a specific cylinder, like an ignition coil or fuel injector failure code and repair as needed. Once the repairs have been made clear the trouble codes and recheck system. If a trouble code is present but does not pertain to the immediate problem like an EVAP failure code it must be checked. The reason we repair non-related codes is if the component is vacuum driven, it might be leaking causing a lean mixture code. If no trouble codes (besides the lean mixture codes) are present proceed to the next step.
    *
      Step 2: If your engine is running rough with no additional trouble codes it will produce a lean mixture DTC (diagnostic trouble code). You must determine what is causing the engine misfire. Please follow this link to troubleshoot the problem, engine misfires If your engine is running ok proceed to the next step.
    *
      Step 3: The exhaust system is used to transfer exhaust gases to the rear of the vehicle. If an exhaust leak is present before the oxygen sensors it can cause the sensor to produce a false reading. You might say a leak will not affect the reading because the exhaust is simply leaking out. The problem is that theory is not exactly true. Engine exhaust is produced in pulses as the cylinder's fire. When the exhaust valve opens pressure is created in the exhaust system while the spent mixture exits the combustion chamber. But then a vacuum condition in the exhaust is created after the exhaust valve closes.  This vacuum condition can draw raw oxygen from outside of the system and cause a false reading. To inspect for an exhaust leak, start with a cold engine. Then have a helper start the engine and hold the idle at about 1500 rpm. Next, try to listen for any exhaust noises coming from any part of the exhaust system including the exhaust manifold and head pipe. Also look for black soot at any point in the system as this can be the source of an exhaust leak. If an exhaust leak is detected repair leak and recheck system. If no exhaust leak is detected continue to the next step.
    *
      Step 4: The oxygen (O2) sensor is designed to deliver feedback voltage to the PCM. If the sensing element fails it will not deliver the proper feedback information causing a lean mixture code. To test the oxygen sensor follow this link - How to test an oxygen sensor.


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## Don2222

Hello

My car is a Toyota Solara V6 and I am not sure whether I fall into section 1 or 2?

Should I change the Vacuum Booster or look at more vacuum hoses??
Not sure where the Air Intake Boot is? Does anyone know??

Diagnostics Continued:
http://www.2carpros.com/articles/repair-lean-mixture-codes-p0171-or-p0174-on-some-manufacturers

Section 2 - Lean mixture code for both bank 1 and bank 2 (lean system code) (bank 1 only on 4 cylinder engines)

(Note: if you have trouble codes for both primary oxygen sensors lean, the chances both sensors have failed are remote. The problem is somewhere else.)

    *

      Step 1: The correct fuel delivery is essential for proper engine operation. This means if the fuel delivery is impaired for any reason it can cause a lean mixture code. The main reasons for this condition are plugged fuel filter or weak fuel pump operation. To inspect the fuel filter follow this link, how to change a fuel filter.
    *

      Step 2: Your engine is designed to run on specific values, if there are no codes besides a lean mixture code and the engine is running ok the problem is a sensing value problem. A MAF (mass air flow) sensor is famous for causing such a problem. Example: Let's say the engine is running at 2100 RPM at any particular time. When a MAF fails it sends feedback information to the PCM that the engine is running at 1800 RPM so the computer will lean down the mixture. But the engine is running at 2100 rpm so the mixture is detected lean by the oxygen sensor and the computer will illuminate the CEL (check engine light). There are a few main reasons the MAF reading can be incorrect. First the air intake boot could be cracked or ripped allowing non-metered engine air intake to be consumed. Or the MAF fails because the sensing element inside the sensor becomes contaminated from impurities from the air the engine consumes. Sometimes this element can be cleaned with an aerosol cleaner such as MAF cleaner. I have had limited success cleaning the MAF sensor, replacement at this point is best. Repair or replace failed components as needed and recheck the system. If your engine does not use a MAF continue to the next step.
    *

      Step 3: Your engine is designed to run on its ability to hold vacuum. If vacuum is allowed to leak it will cause a lean mixture condition. Vacuum hoses are typically connected to the engine intake manifold and will supply engine vacuum to various accessories like power brakes. Some cars are designed with a larger vacuum transfer hose like Ford that connects the intake manifold to the IAC (idle air control) motor. A broken or dilapidated vacuum line or air intake boot can cause the engine to lose vacuum which will cause a lean mixture code. Inspect all engine and accessory vacuum lines to look for missing, torn or dilapidated lines and replace as needed. Also have a helper rest their foot on the gas pedal just enough to keep the engine running. Check the engine when it is running to listen for any whistling noise coming from the engine that is not usually present. Follow the noise and inspect vacuum lines in that area. In addition when the engine is running it will pull inward a broken or weak piece of the hose to create a larger vacuum leak. Check the integrity of all vacuum hoses at each end of the hose. Typically this is where a vacuum hose fails. Replace any vacuums hoses that have failed, clear codes and recheck system.

The pic below is not exactly like the one in my care but I get the idea.


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## kettensÃ¤ge

Sorry to hear this, thought it was done. 

Have the code re read to be sure it is the same problem, may be something unrelated. 

According to your first post you would be bank 1 or section 1. The bank refers the the left or right side of a v-type engine.
It has detected the problem on the side of the engine that cyl#1-3-5 is. Probably the row of cylinders closest to the radiator but verify to be sure. If it was bank 2 it would be on the 2-4-6 cyl side. 

There is an 02 sensor on each side and maybe a third behind the catalytic converter to monitor it's efficiency. 

Since inline engines only have 1 bank of cylinders it can't show a bank 2 problem. 

Did you change the primary 02 sensors, are they original, how many miles? If they are past their reccomended service time change them. It won't be a waste of money since they are due for service and it may solve the problem. If not you may need to find someone with a good scan tool to interpret the data stream.

Does the brake booster hold vacuum? Can you go out and step on the brake 30 mins. after shutting the car off and still have power assist for 1 press of the brake pedal? There are tests for these things to determine their condition before you replace them.

Look at the ignition system, spark plug/wires and coil(s) on bank one. A misfire will show up as a lean condition as stated in your post.


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## Don2222

Hello Kettensage

Thanks again for your reply.

Well I may have fixed it again I appreciate your post because it made me keep thinking in the right direction. I did have the code checked again by AutoZone and got the P0171. I also went back to Toyota to see if they would check it again since I purchased their OEM Mass Air Flow meter for $231.00 and they said because they did not fix the car, I would have to pay another $94.00 !! If I did have them fix it they told me it would be approx. $2,500  I said that I cannot afford it, times are tough and walked out. Luckily I did not say what I was thinking!! ((#$#`~@#$)) 

So I appreciate your recent reply and found on my own that Bank 1 Cylinders 1,3,5 are farthest away from the firewall (Close to the radiator)and I do remember getting new spark plug wires and plugs about 1.5 years ago. So I went back to looking at vacuum lines and replaced another small one but the old one did not look like it was leaking. Then I found this! See pic below. A larger vacuum line that went from the Air Intake Hose on the opposite side where the MAF was plugged in, that was missing a spring clamp!! So I took the hose to Advanced Auto parts. The hose had one end slightly larger than the other and I am not paying Toyota Big Bucks for a new one since it was not in bad shape. So I purchased 4 hose clamps in a pack for $2.50 and came home and put 2 in by removing the one where the blue arrow is pointing and adding in one where the yellow arrow is pointing. The yellow arrow points to where the missing clamp was!! Of course this vacuum hose with the missing clamp is connected to the back side of the engine which is Bank1 !!

*Also I learned the Engine Light On or "CEL ON Sticker Trick"! Take off the Positive Battery Terminal for 1 min to reset the CEL. Doing this does clear the error code but puts the 5 monitors in the computer to incomplete and the ready flag to "Not Ready" so if the Emissions was tested at this time it would still fail. This is so people will cheat a and get a sticker. So now the computer has to be taken through 1 complete drive cycle to set the monitors to complete and change the ready flag to "Ready", So for the Toyota Solara a drive cycle I found that completes all the monitor drive patterns is as follows: I drive the car 25 miles half highway and half city stop and go including a minimum speed of 55 mph for a min of 3 mins and down to 30 MPH without breaking and back up to 55 MPH for 3 - 5 mins to change the ready flag to "Ready" and then you have approx 1 or 2 miles to go get the sticker before the code and light come back if the failure still exists I did this last year and it works *
  So I just drove the car 25 miles and then another 5 miles after fixing the vacuum hose and the CEL did not come back on!! I think the drive cycle is nit completed, So wish me luck and I will drive it more and report back soon. I need a sticker this month

I just found Toyota Technical Service Bulletin TSB-EG003-02 Readiness Monitor Drive Patterns.
This explains how to drive the car after one of the emission systems was fixed to get the computer into "Ready" for emissions testing

Yellow arrow shows where original spring clamp was missing, that now has the new radiator type screw down clamp.
Blue arrow shows spring clamp replaced by radiator type clamp!


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## Don2222

Hello

Well I went about 10 more miles (Total 25) since resetting the Check Engine Light (CEL) is ON by removing the Pos. Battery Terminal for 1 min. The CEL came on again

So I went under the hood again and as I am becoming more and more familiar with the vacuum hoses on this car I spotted something else!!

Apparently it is much easier to change the air filter if this vacuum hose is removed, but it should have been put back!!
Also no clamp!! So I added 2 screw clamps and removed one spring clamp and the other end

So time to reset and try again!!

See Pics 1, 2 3 below:


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## kettensÃ¤ge

Hey Don,
Glad I could help.


I had 1 of those air cleaner lines like that on the wife's Subie give me fits. It wouldn't even idle. 
It looks like that is in a place where unmeasured (after the MAF) air could get in. 

I hope that is the final fix for this problem. Let me know what happens.


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## Don2222

Hello kettensÃ¤ge

Unfortunately that did not fix it. The CEL came back on after 22 miles of stop and go driving.

The good news is that I found one last bad part that can throw that P0171 code. The Vacuum Booster behind the Master Brake Cylinder. There is a posting on the SolarGuy forum that tells us after replacing that Vacuum Booster it resolved the Code.

See  http://www.solaraguy.com/viewtopic.php?f=54&t=50115&start=0

     Here is what the link above says
It was my Brake booster, that was causing a vacuum leak.
  The first shop I went to, told me it would be $650 ($325 for BB + $325 for Labor) to swap it out,  . For 8 bolts?! 
Next shop said it would be $180 bucks if I find the part myself and he couldn't do it that day (I needed it same day for vehicle inspection)
  I finally used a hook up at a wholesale parts store (Buy Wise) and got the Brake Booster for $228.
Went to my father's mechanic, he said he'll install it for a $100 and get it done before the end of the day. No more hissing, no CEL yet.

Also, The Toyota tech told me that vacuum booster can go bad and make the P0171 error code! He also told me how to test it to see if the booster is bad.
1. If it makes a hissing or wind sound when stepping on the brake. - Yes it Does!!
2. After turning off the engine with the key, there should be one last easy push of the brake pedal down to the flow. No it was hard!!

So I will be having this fixed next week


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## Don2222

Hello

Well the vacuum booster part was ordered. Still waiting for it to come in.

So in summary the best way to fix this issue is by starting with the cheapest parts first.
Toyota CEL Check Engine Light Error Code P0171

Here is the way I should have gone.

1. Engine Vacuum Lines

a. Check or replace the two vacuum lines that go from the engine to the vacuum reserve canister under the battery.
You can use American 5/32 line but if your can get the smaller outside diameter foreign line, the engine holding clips will still work and keep the line away from the hot motor.

b. Check or replace the vacuum booster line from the engine to the vaccuum booster behind the master cylnder.
American 3/8 Vacuum booster hose will work fine.

c. Check all other engine vacuum lines but the above two are the common cause.

2. MAF -Mass Air Flow Sensor.
Make sure you have the additional error codes below. Use OEM because a refurbished part will not give the performance!
P0100 - Air Flow Meter
P0110 - Air Flow Malfunction
Toyota OEM MAV part is $231.00 and makes the car perform like new, but the Re-furbished MAV for $70.00 will give more trouble!

3. Flex Line Exhaust Leak before the down stream O2 Sensor.
Should also get a P0420 error code to turn the light on.
Aftermarket part is $50.00 while the OEM Toyota part is part of the catalytic converter and costs $2,000.00
It must be done anyway for inspection if there is an exhaust leak here. The aftermarket works fine.

4. Low Fuel Pressure
Replace Toyata inline fuel filter on the driver's side inside front fender near the battery. 
Toyota style replacement $65.00 at auto parts store. You can probably install an inexpensive inline real cheap here!
This is not so easy since the metal fuel line screws right into the filter!
The easiest way is to cut the fuel line and remove the other side which is a rubber hose.
Install the new Fuel filter by unscrewing the old line from the old filter and screwing it onto the new filter.
Then add a rubber fuel line to connect the severed ends together!

5. Misfire
Replace all spark plugs and wires. The car will run better if they are old anyway.
My wires crumbled from being old and brittle!

6. Vacuum Booster Behind the Master Brake Cylinder.
Before replacing this part there are 2 simple tests to make sure it is bad.
A. When driving and stepping on the brakes you will hear a hiss sound of the leaking air.
B. After turning the key off the brake Pedal will not press down easily one last time!
    Compare with a working car and you will feel the difference!
Aftermarket booster is $500.00 and made to last a long time OEM Toyota is $900.00 and obviously does not last long!

7. Replace O2 Sensors. You also get better gas mileage! After market O2 sensors made for Toyota usually work.
    Replace the 2 upstream sensors on the exhaust manifolds
    Replace the 1 downstream O2 sensor after the catalytic converter. (You can use a Dummy Sensor here if you can find one!)
Nice removal tool that works with an Air Chisel!
 http://www.thetoolwarehouse.net/p-3128-lisle-43900.aspx


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## Don2222

Hello

Well, I got a used Toyota Vacuum Booster for $170.00 from Arizona and had it installed today. No more hissing when braking! We will see if that fixes it?
A little cheaper than $900.00 for the Brand New OEM Toyota part!


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## Don2222

Hello

Well the new vacuum booster finally fixed the P0171 code.

Interesting because I took it on my newly developed Drive Cycle after the booster was installed.

New Drive Cycle for Toyota

With the gas tank between 1/2 and 3/4 full to change the Monitors for emissions in the carâ€™s computer from â€œNot Readyâ€ to â€œReadyâ€

Drive the car 25 miles half highway and half city (stop & go) and while on the highway include a minimum speed of 55 mph for a min of 3-5 mins and then coast to a stop on the side of the road and keep engine idling for 3-5 mins without breaking and then back up to 55 MPH for 3 - 5 mins.

When I took it back to the shop we put the Genesis Code Scanner on the car and found only 1 Monitor - EVAP system was not ready.

Now the EPA standard states it is OK to have 1 monitor "Not Ready" for 2001 and newer cars and 2 Monitors "Not Ready" for cars 1996-2000. So having a 1999 I was all set. Sure enough< I got my inspection sticker. CASE CLOSED.

See pics below of BAD VACUUM BOOSTER


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## jlove1974

When I had P0171 and P0174 (it's a V8) on our 2003 Suburban, I checked for vacuum leaks. The fuel pump had been changed 13 months beforehand, so I assumed it was an air leak....
WRONG. After replacing various fuel and vacuum parts (and using a AZ MAF sensor w/ a new delco sticker on it), it turned out to be the budget Airtex pump only putting out 20psi (should be around 40-45 psi) fuel pressure.
I put a Delco pump on it and VOILA no more lean code.

OBD-II sucks, IMO. it's too darn picky LOL. The truck ran OK, but I couldn't get it inspected for a month until I fixed it


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## Don2222

Hi jlove

Thanks for the info, I replaced the gas filter but that did not fix it.

Well glad our ordeals are over


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## jlove1974

I guess so. My next vehicle acquisition is a 2000 Honda Odyssey (to relieve the pain at the pump the 'burb is currently causing!) with 178K miles.
It has a code on the dash which says the transmission is basically dead. Good thing I am only paying $2000 for it. And the tranny w/ warranty is $1K.

We'll see if the Honda is any more reliable than the Chevy. Somehow, I doubt it. After their numerous transmission problems in these vans, I would
only buy one with a rebuilt transmission w/ warranty. Oh and a timing belt/water pump job done recently.

Don, I would recommend if you don't already have one of these in your toolkit:

http://www.harborfreight.com/fuel-injection-pump-tester-92699.html it's worth it's price many times over for fuel injected cars. 

Also the cheap CAN OBD-II tester I use (was $39 on sale) http://www.harborfreight.com/can-obdii-code-reader-with-multilingual-menu-98568.html


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## TMonter

jlove1974 said:
			
		

> I guess so. My next vehicle acquisition is a 2000 Honda Odyssey (to relieve the pain at the pump the 'burb is currently causing!) with 178K miles.
> It has a code on the dash which says the transmission is basically dead. Good thing I am only paying $2000 for it. And the tranny w/ warranty is $1K.
> 
> We'll see if the Honda is any more reliable than the Chevy. Somehow, I doubt it. After their numerous transmission problems in these vans, I would
> only buy one with a rebuilt transmission w/ warranty. Oh and a timing belt/water pump job done recently.
> 
> Don, I would recommend if you don't already have one of these in your toolkit:
> 
> http://www.harborfreight.com/fuel-injection-pump-tester-92699.html it's worth it's price many times over for fuel injected cars.
> 
> Also the cheap CAN OBD-II tester I use (was $39 on sale) http://www.harborfreight.com/can-obdii-code-reader-with-multilingual-menu-98568.html



I have an odyssey and can speak to the transmission issue.

First be very careful with a transmission that only costs $1000, that price is very suspect. My total rebuild on my 2001 Odyssey cost me about $2800 with removal/replacement a cooler install and a inline filter addition.

The biggest problem with Odyssey's has been the trans fluid they use. It's not synthetic so it has a tendency to overheat easily and burn the fluid. I recommend a full synthetic fluid like Amsoil or equivalent. If you want to start a new thread I can give some more suggestions as I've gone through this whole transmission issue in detail. 

Average transmission life on an odyssey with a good rebuild and regular maintenance seems to be about 175K+ miles.


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## jlove1974

The price is not including labor. It'll be around $1500 w/ full synthetic fluid and labor (a friend who is a ATRA certified trans tech).
He rebuilt an electronic 4wd transfer case for us last spring that was better than factory new when I got it back. I did the install on that one.

I didn't feel like pulling the tranny w/o a lift so I figured $500 for labor was a steal....compared to what Honda charges.

I'm planning on putting another 100-150K on this one, hopefully the gas situation will be settled by then (approx. 3 years).

I will be doing the timing belt/water pump myself after I get the van back from the trans rebuild. Looks about like what my mazda KL V6 was, a PITA


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## TMonter

jlove1974 said:
			
		

> The price is not including labor. It'll be around $1500 w/ full synthetic fluid and labor (a friend who is a ATRA certified trans tech).
> He rebuilt an electronic 4wd transfer case for us last spring that was better than factory new when I got it back. I did the install on that one.
> 
> I didn't feel like pulling the tranny w/o a lift so I figured $500 for labor was a steal....compared to what Honda charges.
> 
> I'm planning on putting another 100-150K on this one, hopefully the gas situation will be settled by then (approx. 3 years).
> 
> I will be doing the timing belt/water pump myself after I get the van back from the trans rebuild. Looks about like what my mazda KL V6 was, a PITA



Make sure you add a good inline filter like a Magnafine and a large transmission cooler. The new transmission also includes a new Torque converter I hope.


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## Don2222

Hello

Well folks, it has been a month now and the MIL (Malfunction Illumination Lamp) Alias CEL (Check Engine Light) is NOT ON !!

The used Vacuum Booster really fixed it!!


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## heat seeker




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## Don2222

Hello

Well I learned alot from this ordeal. The most important fact is the EPA emissions testing alows 1996 to 2000 cars to have 2 emission system monitors in your car's computer in "Not Ready" status and 2001 cars and above can have 1 emission system monitor in "Not Ready" status and PASS emissions testing. This means if you reset the car's computer by temporarily removing one of the battery terminals. You can see the monitors go to "Ready" status with an inexpensive code checker as you drive the car. So if you have a problem in the evaporator system which is the last monitor to go to "Ready" status, just get the emissions tested after the other monitors are in "Ready" status and you will pass the emissions testing If you have a pre-2001 car then the system before the evaporator system can also be broken and still get a sticker!! Also the drive cycle to get these monitors "Ready" is by driving the car approx 12 miles on the highway and then 12 miles back on a regular stop and go route! Then you will be ready for emissions testing after reseting the car's computer!!


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