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P0171 Error Code


R.Holmes
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High guys, & Gals, I know this is not a new topic but I have searched the forum and read all the threads (that I could find) about the P0171 error code and tried all the fixes (?) but the code keeps coming up. This is what I have done so far

Cleaned MAF, Didn't work

Repalaced MAF, IAT sensor. Didn't work ( IAT is incorperated in the MAF sensor)

Checked ECT sensor and it is working properly

Replaced Coils, Didn't work

I clear the code and Check Engine light and it stays off for about 1/2 hrs of driving and it comes back on.

Can anyone offer me any more suggestions on how to solve this problem? Any suggestion will be greatly appreciated.

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DTC P0171 System too Lean (Fuel Trim)

P0171

When the air fuel ratio feedback is stable after engine warming

up, the fuel trim is considerably in error on the RICH side

(2 trip detection logic)

Air intake (hose loose)

Fuel line pressure

Injector blockage

Heated oxygen sensor (bank 1, 2 sensor 1) malfunction

Mass air flow meter

Engine coolant temp. sensor

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DTC P0171 System too Lean (Fuel Trim)

P0171

When the air fuel ratio feedback is stable after engine warming

up, the fuel trim is considerably in error on the RICH side

(2 trip detection logic)

Air intake (hose loose)

Fuel line pressure

Injector blockage

Heated oxygen sensor (bank 1, 2 sensor 1) malfunction

Mass air flow meter

Engine coolant temp. sensor

Checked all hoses Ok

Replaced fuel pump and filter a few months back

Ran injector cleaner in two tanks of gas, even used higher octane fuel

Changed MAF

Engine coolant temp sensor seems to be working properly according to engine manual check out procedures

Have not checked Heated Oxygen sensor. Will do that tomorrow.

Thanks.

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  • 2 weeks later...
The last time I saw this code was on a camry and it was the o2 sensor

Update on my p0171 code problem: After weeks of agonizing troubleshooting to solve this agravating code, I finally solved the culprit.!!!

After exausting all the suggestions recieved from fellow members and talking to mechanics (each mechanic, different solution) I found where the problem was. I sat back and analized what was going on.Checked ok(A/F,Maf. Map etc. etc.) All vacumn hoses, canister, fuel pressure checked ok. I was ready to pull my hair ( What little I have left) Most indication of the lean fuel mixture was vacumn leak somewhere. Internally or intake? I very faintly hear a hissing sound near the canister, checked it (and hoses again) all ok. Where is there a very high vacumn?? Brake booster!!!!!! Cleared the code and removed the vacumn hose to the booster. Code emmediately came on. Plugged the hose and the code was gone. (No power brakes of course!!!) Code stayed off while idleing for about an hour. Replaced the booster and have driven car for about a week and the code has not returned. Apparently I had a pin hole leak in the diafram of the booster. Just enough to trigger the code. Hopes this helps someone else with the P0171 code.

PS: A stetoscope would have been helpful in detecting the leak.

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good work. did you use the overhaul kit. how much is the part. is it a diy. is this a common issue.

Most of it was trial and error. With suggestions of what the problem might be from members of the forum, I just started elimenating .

After getting frustrated, I sat back and re-analized what I was doing. That is when I found the problem. I bought a new booster but had a problem with the clearence adjustment between the booster and the master cyclinder (Adjustment was very tight). I returned it and had my booster rebuilt for $175. After market (new) was $190 and dealer quoted $600. Time quoted was three hrs. at $75. per. I did it in 1.5 hrs. and a half hr bleeding the brakes.Other than that. it was just time consuming. Had to remove the air cleaner and canister and master cyclinder and connections to the brake pedel. That was the hardest. (Tight fit space)

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  • 3 years later...
good work. did you use the overhaul kit. how much is the part. is it a diy. is this a common issue.

Most of it was trial and error. With suggestions of what the problem might be from members of the forum, I just started elimenating .

After getting frustrated, I sat back and re-analized what I was doing. That is when I found the problem. I bought a new booster but had a problem with the clearence adjustment between the booster and the master cyclinder (Adjustment was very tight). I returned it and had my booster rebuilt for $175. After market (new) was $190 and dealer quoted $600. Time quoted was three hrs. at $75. per. I did it in 1.5 hrs. and a half hr bleeding the brakes.Other than that. it was just time consuming. Had to remove the air cleaner and canister and master cyclinder and connections to the brake pedel. That was the hardest. (Tight fit space)

I am having the same problems with my 1999 ES300. When your P0171 (bank1) code first started coming on, did you "feel" any problem with your brakes? With the engine running, I pump my brake pedal multiple times, and it always feels spongy. When I turn the engine off and pump my brakes, the pedal does get tight. Is this normal?

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The last time I saw this code was on a camry and it was the o2 sensor

Update on my p0171 code problem: After weeks of agonizing troubleshooting to solve this agravating code, I finally solved the culprit.!!!

After exausting all the suggestions recieved from fellow members and talking to mechanics (each mechanic, different solution) I found where the problem was. I sat back and analized what was going on.Checked ok(A/F,Maf. Map etc. etc.) All vacumn hoses, canister, fuel pressure checked ok. I was ready to pull my hair ( What little I have left) Most indication of the lean fuel mixture was vacumn leak somewhere. Internally or intake? I very faintly hear a hissing sound near the canister, checked it (and hoses again) all ok. Where is there a very high vacumn?? Brake booster!!!!!! Cleared the code and removed the vacumn hose to the booster. Code emmediately came on. Plugged the hose and the code was gone. (No power brakes of course!!!) Code stayed off while idleing for about an hour. Replaced the booster and have driven car for about a week and the code has not returned. Apparently I had a pin hole leak in the diafram of the booster. Just enough to trigger the code. Hopes this helps someone else with the P0171 code.

PS: A stetoscope would have been helpful in detecting the leak.

The last time I saw this code was on a camry and it was the o2 sensor

Update on my p0171 code problem: After weeks of agonizing troubleshooting to solve this agravating code, I finally solved the culprit.!!!

After exausting all the suggestions recieved from fellow members and talking to mechanics (each mechanic, different solution) I found where the problem was. I sat back and analized what was going on.Checked ok(A/F,Maf. Map etc. etc.) All vacumn hoses, canister, fuel pressure checked ok. I was ready to pull my hair ( What little I have left) Most indication of the lean fuel mixture was vacumn leak somewhere. Internally or intake? I very faintly hear a hissing sound near the canister, checked it (and hoses again) all ok. Where is there a very high vacumn?? Brake booster!!!!!! Cleared the code and removed the vacumn hose to the booster. Code emmediately came on. Plugged the hose and the code was gone. (No power brakes of course!!!) Code stayed off while idleing for about an hour. Replaced the booster and have driven car for about a week and the code has not returned. Apparently I had a pin hole leak in the diafram of the booster. Just enough to trigger the code. Hopes this helps someone else with the P0171 code.

PS: A stetoscope would have been helpful in detecting the leak.

I am having the same problems with my 1999 ES300. When your P0171 (bank1) code first started coming on, did you "feel" any problem with your brakes? With the engine running, I pump my brake pedal multiple times, and it always feels spongy. When I turn the engine off and pump my brakes, the pedal does get tight. Is this normal?

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I am having the same problems with my 1999 ES300. When your P0171 (bank1) code first started coming on, did you "feel" any problem with your brakes? With the engine running, I pump my brake pedal multiple times, and it always feels spongy. When I turn the engine off and pump my brakes, the pedal does get tight. Is this normal?

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  • 11 months later...

Had codes P0171 and P0174 in a 2001 GS300 with 85K miles. enigne too lean banck 1 and bank 2. Car runs sluggish, wont pass smog test.

MAF resistance measured OK. MAF looks dirty. Spray clean with carburetor cleaner, did not help.

Swapped in the same MAF from another Toyota. The P0171 and P0174 problem was fixed. Car runs smooth and powerful. Passed smog test.

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