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Discussion Starter #1
Anyone have some additional tests to help diagnose this trouble code in bank 1 on 2010 Impala w/3.5L?


Trouble Code PO172
Fuel Sys 1 – Closed
Calc Load – 50.2%
Coolant - 187° F
ST FTRM1 (%) ` 0.0
LT FTRM1 (%) -25.8
MAP (“HG) 23.0
Eng Speed (RPM) 1347
VEH Speed (MPH) 52
IGN ADV (°) 24.0°
IAT (°F) 52
MAF (LB/M) 2.44
ABSLT (TPS) % 33.3
EVAP Purge 0.0
Fuel Level 44.3%
CLR TRPS 2
CLR DIST (MI) 3
EVAP VP(H2O) -0.231
BARO PRS (“HG) 29.5
CAT Temp11 (°F) 1148
VPWR (V) 14.883
ABS Load (%) 40.8
CMD EQ RAT 0.999
OUT Temp (°F) 50
ABS TPS B (%) 33.3
ACC POS D (%) 28.6
ACC POS E (%) 14.5
THROT CMD (%) 27.8
ALCOHOL (%) 63.5

Also I did a Fuel Pressure Test on the fuel rail and the pressure stayed @ 55 PSI running and during a 10 minute shutdown. If the fuel pressure regulator was faulty i believe i would get a rich condition in both banks?
I'm not getting any misfire codes to show a cylinder is not firing on the rich bank.
The fuel system is also a return-less fuel system.
My thought is because of the negative LTFT would be a rich condition because of to much fuel? Could it be a faulty injector on bank 1? If it was a positive reading my thought was a vacuum leak?
The other two parameters that i question are MAP sensor seems slightly high @ 23.0 and the Alcohol % is content , I think this was a bad test, should i re-test after LTFT returns to normal?

Thoughts?
 

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Yup, you need to check the Long Term Fuel Trim % which in your case is way low (-25.8%)...
That means your car has cut fuel as much as it can to compensate for the rich condition, and now it can't cut fuel any further so the code appears.
What this does is confirm the code as legitimate, your car is in fact running rich (or at least the sensors have determined that it is).

Your most likely causes:
Dirty or Faulty MAF
Dirty or Faulty Throttle Body
Worn spark plugs
Weak spark plug wires
Vacuum Leak

Your somewhat less likely Causes:
Faulty oxygen sensor
Leaky fuel injectors allowing too much fuel into the combustion cylinders
Stuck fuel pressure regulator
Faulty coolant temperature sensor
Faulty coolant thermostat

There is nothing beyond that I can tell you...
The best I can do is tell you start replacing parts until the code goes away.
I would do it one at a time so you can backtrack if necessary.
 

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Discussion Starter #4
Sidemouse,
I cleaned the MAF and also the reading is within manufacturers range - MAF 2.44
The throttle body was thoroughly cleaned with almost a full can of cleaner.
The plugs may be worn, but once the car is warm it runs great, no misfires or any additional codes.
I hate to start throwing parts at it, I’d like to narrow it down. I’m going to do another fuel pressure test and try and find a fuel line to pinch off and see if the pressure bleeds off, that would indicate fuel rail or injectors I believe.

Bill58
No I’ve only used standard 87 octane which says E10 on the pump. I agree that reading is super high and I don’t know any other way to reset fuel composition and fuel trims, unless I go to the dealer?
 

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Bill58
No I’ve only used standard 87 octane which says E10 on the pump. I agree that reading is super high and I don’t know any other way to reset fuel composition and fuel trims, unless I go to the dealer?
Don't have to go to to the dealer but do need to find a shop with dealer level equipment. ECM thinks you have 63% alcohol so it's increasing injector duty cycle. With E10 engine will run rich.
 

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Discussion Starter #6
Bill58,
Do you think that only the ECM is the thing at fault, and the rich condition will return to normal after reprogramming?
 

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Bill58,
Do you think that only the ECM is the thing at fault, and the rich condition will return to normal after reprogramming?
GM is at fault, there isn't a alcohol sensor. They cheep-out by calculating the alcohol content using the O2 sensors instead of actually measuring % content.
A good shop may reflash your ECU if there are any updates to avoid future problems.
I would get it taken care of soon. Your cat is eating all the extra fuel and can over heat causing damage the cat.
 

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Sidemouse,
I cleaned the MAF and also the reading is within manufacturers range - MAF 2.44
The throttle body was thoroughly cleaned with almost a full can of cleaner.
The plugs may be worn, but once the car is warm it runs great, no misfires or any additional codes.
I hate to start throwing parts at it, I’d like to narrow it down. I’m going to do another fuel pressure test and try and find a fuel line to pinch off and see if the pressure bleeds off, that would indicate fuel rail or injectors I believe.

Bill58
No I’ve only used standard 87 octane which says E10 on the pump. I agree that reading is super high and I don’t know any other way to reset fuel composition and fuel trims, unless I go to the dealer?
I cleaned my MAF too, didn't change anything...
Then I replaced it, and that fixed the problem.

Just saying...
 

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I also have the P0172 code. 2008 Impala 3.5L Vin K

Observing live data, the engine runs with a bias towards the rich side, but not always so rich as to cause the P0172. Some freeze frame data below.


The sensors (MAP, MAF, ECT, O2) appear to be operating in the desired range. The MAP sensor appears clean. The air filter is clean. The spark plugs were replaced and no improvement was seen.



My system also reports a crazy high Alcohol content, but as this is just calculated I wouldn't expect it to be correct given the rich condition. And it changes all the time (between 40% and 80%). I suspect that if a garage could change it to an appropriate value, it would just calculate and change itself again.



I also have a rough cold start issue - not sure if this is related. The engine will not start and stay started unless I press the accelerator to keep the RPM above 1500 for about 40 seconds. Once warm the car runs and will start without issue. I could not find any vacuum leaks. DBStrings, do you have a cold start issue?



Trouble Code Triggering Freeze Frame: P0172: System Too Rich Bank 1


Freeze Frame Data:
· PID : Description : Value
· 03 : Fuel System Status : Closed loop - using all oxygen sensor(s) as feedback for fuel control
· 04 : Calculated Engine Load Value : 29.0 %
· 05 : Engine Coolant Temperature : 92 °C, 198 °F
· 06 : Short Term Fuel Trim Bank 1 : -5.5 %
· 07 : Long Term Fuel Trim Bank 1 : -30.5 %
· 0B : Intake Manifold Absolute Pressure : 41.0 kPa, 12.1 inHg
· 0C : Engine RPM : 1415 rpm
· 0D : Vehicle Speed : 81 km/h, 50 MPH
· 0E : Timing Advance for #1 cylinder : 41.5 °
· 0F : Intake Air Temperature : 9 °C, 48 °F
· 10 : Mass Air Flow Rate : 11.41 g/s, 1.51 lb/min
· 11 : Absolute Throttle Position : 30.2 %
· 1F : Run Time Since Engine Start : 203 seconds

· 2E : Commanded Evaporative Purge : 0.0 %
· 2F : Fuel Level Input : 76.5 %
· 30 : # of Warm-ups Since Codes Cleared : 1 #
· 31 : Distance Traveled Since Codes Cleared : 45 km, 28 mile
· 32 : Evap. System Vapor Pressure : -52.8 Pa, -0.2 inH O ₂
· 33 : Barometric Pressure : 98 kPa, 29 inHg
· 3C : Catalyst Temperature Bank 1 - Sensor 1 : 660.0 °C, 1220.0 °F
· 42 : Control Module Voltage : 14.343 V
· 43 : Absolute Load Value : 23.1 %
· 44 : Commanded Equivalence Ratio : 0.999 λ
· 45 : Relative Throttle Position : 16.1 %
· 46 : Ambient Air Temperature : -6 °C, 21 °F
· 47 : Absolute Throttle Position B : 30.2 %
· 49 : Accelerator Pedal Position D : 27.5 %
· 4A : Accelerator Pedal Position E : 13.3 %
· 4C : Commanded Throttle Actuator : 23.1 %
· 52 : Alcohol Fuel % : 74.9 %
 

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Discussion Starter #10
Yes. On initial start-up i also need to increase the RPM's otherwise it will stall.

Just as BILL 58 said, GM is calculating the alcohol content using the O2 sensors instead of actually measuring % content. There isn't a alcohol sensor

I'm going to make a few calls today and see if i can find a shop to Reset Fuel Composition.

I also have the P0172 code. 2008 Impala 3.5L Vin K

Observing live data, the engine runs with a bias towards the rich side, but not always so rich as to cause the P0172. Some freeze frame data below.


The sensors (MAP, MAF, ECT, O2) appear to be operating in the desired range. The MAP sensor appears clean. The air filter is clean. The spark plugs were replaced and no improvement was seen.



My system also reports a crazy high Alcohol content, but as this is just calculated I wouldn't expect it to be correct given the rich condition. And it changes all the time (between 40% and 80%). I suspect that if a garage could change it to an appropriate value, it would just calculate and change itself again.



I also have a rough cold start issue - not sure if this is related. The engine will not start and stay started unless I press the accelerator to keep the RPM above 1500 for about 40 seconds. Once warm the car runs and will start without issue. I could not find any vacuum leaks. DBStrings, do you have a cold start issue?



Trouble Code Triggering Freeze Frame: P0172: System Too Rich Bank 1


Freeze Frame Data:
· PID : Description : Value
· 03 : Fuel System Status : Closed loop - using all oxygen sensor(s) as feedback for fuel control
· 04 : Calculated Engine Load Value : 29.0 %
· 05 : Engine Coolant Temperature : 92 °C, 198 °F
· 06 : Short Term Fuel Trim Bank 1 : -5.5 %
· 07 : Long Term Fuel Trim Bank 1 : -30.5 %
· 0B : Intake Manifold Absolute Pressure : 41.0 kPa, 12.1 inHg
· 0C : Engine RPM : 1415 rpm
· 0D : Vehicle Speed : 81 km/h, 50 MPH
· 0E : Timing Advance for #1 cylinder : 41.5 °
· 0F : Intake Air Temperature : 9 °C, 48 °F
· 10 : Mass Air Flow Rate : 11.41 g/s, 1.51 lb/min
· 11 : Absolute Throttle Position : 30.2 %
· 1F : Run Time Since Engine Start : 203 seconds

· 2E : Commanded Evaporative Purge : 0.0 %
· 2F : Fuel Level Input : 76.5 %
· 30 : # of Warm-ups Since Codes Cleared : 1 #
· 31 : Distance Traveled Since Codes Cleared : 45 km, 28 mile
· 32 : Evap. System Vapor Pressure : -52.8 Pa, -0.2 inH O ₂
· 33 : Barometric Pressure : 98 kPa, 29 inHg
· 3C : Catalyst Temperature Bank 1 - Sensor 1 : 660.0 °C, 1220.0 °F
· 42 : Control Module Voltage : 14.343 V
· 43 : Absolute Load Value : 23.1 %
· 44 : Commanded Equivalence Ratio : 0.999 λ
· 45 : Relative Throttle Position : 16.1 %
· 46 : Ambient Air Temperature : -6 °C, 21 °F
· 47 : Absolute Throttle Position B : 30.2 %
· 49 : Accelerator Pedal Position D : 27.5 %
· 4A : Accelerator Pedal Position E : 13.3 %
· 4C : Commanded Throttle Actuator : 23.1 %
· 52 : Alcohol Fuel % : 74.9 %
 

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Discussion Starter #11
Quick Update everyone,
I called around my area and found a couple repair shops that have a TECH-2 scanner or equivalent to what the dealer uses. The cost to perform Fuel Composition reset (Alcohol %) varies from $99.00 +tax to $124.99 +tax
No-one can fit me in until early next week, I'll post if the reset does cure the issue.

One repair shop told me to remove the negative battery cable overnight and it should clear/reset everything. NOPE! It was off initially but came back on during my drive to work.
 

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Discussion Starter #14
!UPDATE!

OK I did have a the local shop perform the Fuel Composition Reset a week ago. I wanted to drive it before responding in case the trouble code came back on.

The Reset/Update to the ECU has cleared the trouble code! Using my BlueDriver scan tool the Alcohol Percentage is back at 0% :eek:k3:
All the initial startup issues because of to much fuel have gone away, the car is running great.

FYI the shop has a Snap-On scan tool and they charged me $99.00+tax.
 

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Great news! Be sure to check into this discussion every now and again to let us know if all continues to run well. You might also want to report the alcohol content from your scan tool.
 
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