2017 GMC Sierra 1500 4X4 5.3L (Not Flex) P0172/P0175

[Chris Morris]

Hello,

          I am new here but out of all the reading I have done this place seemed like my best bet at a last hope. I have been having an issue with my truck the least few week.  When it is at idle after being warmed up and/or on a hot day my traction light comes on for a moment and then goes off. After that it seems to downshift early and takes off a bit fast. If I turn off the engine and start it back up it is fine. It has codes stored but the light don't come on a lot and when it does they are gone in a few hours. I have been reading and watching everything I can find and I am now at the point where replacing stuff is going to get expensive. I had a friend hook it up to his scanner and it showed the coolant temp and MAF sensor with faults on top of the P0172/175. So, I have replaced the plugs, wires, MAF, Coolant temp sensor, PCV Valve and have put seafoam in the gas tank. I have also cleaned the MAP/BARO Sensor. I ended up buying a cheap scanner so I could see some live data. I am at the point where I don't know if it is injectors, High pressure fuel pump, fuel pump, or something else I am missing. I will post the numbers I seen while at idle. I would post the pictures but they have too many MB.  On another note there is a hint of gas smell on the oil dipstick. I would say I have better then average ability to work on vehicles myself, I have never been to a shop for anything but the tires and a oil change cause its not worth the time to do it myself. I really appreciate any help that I may be able to get.  Thank you for even taking the time to look at the post. 

 

DTC_CNT (0)

FUELSYS1 (CL)

FUELSYS2 (CL)

LOAD_PCT% (13.7)

ECT (187 F)

SHRTFT1% (-19.5)

LONGFT1% (-35.2)

SHRTFT2% (-21.1)

LONGFT2% (-35.2)

FRP (47.4 psi)

MAP (8.0 inHg)

RPM (562)

VSS (0 mph)

SPARKADV (30)

IAT (91 F)

MAF (0.602 lb/min)

TP (14.5%)

SHRTFTB1S1 (-19.5%)

O2B1S1 (0.110v)

O2B1S2 (0.795v)

O2B2S1 (0.775v)

SHRTFTB2S1 (-21.1%)

O2B2S2 (0.775v)

RUNTM (795 sec)

FRP (484.4 psi)

EVAP_PCT (9%)

FLI (69%)

EVAP_VP (0.052 inHg)

BARO (28.6 inHg)

CATEMP11 (683.60 F)

CATEMP21 (644.00 F)

VPRW (13.870v)

LOAD_ABS (18.2%)

EQ_RAT (0.999)

TP_R (4.3%)

AAT (79 F)

TP_B (14.5%)

APP_D (19.2%)

APP_E (9.4%)

TAC_PCT (5.9%)

 

 

 

 

Edited July 11 by Chris Morris

[asilverblazer]

Quote

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P0171

Fuel Trim System Lean Bank 1

DTC P0172

Fuel Trim System Rich Bank 1

DTC P0174

Fuel Trim System Lean Bank 2

DTC P0175

Fuel Trim System Rich Bank 2

Circuit/System Description

The engine control module (ECM) controls a Closed Loop air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. The ECM monitors the heated oxygen sensor (HO2S) signal voltage, and adjusts the fuel delivery based on the signal voltage while in Closed Loop. A change made to the fuel delivery changes the long and short term fuel trim values. The short term fuel trim values change rapidly in response to the HO2S signal voltages. These changes fine tune the engine fueling. The long term fuel trim values change in response to trends in the short term fuel trim The long term fuel trim makes coarse adjustments to fueling in order to re-center and restore control to short term fuel trim. The ideal fuel trim values are around 0 %. A positive fuel trim value indicates that the ECM is adding fuel in order to compensate for a lean condition. A negative fuel trim value indicates that the ECM is reducing the amount of fuel in order to compensate for a rich condition.

Conditions for Setting the DTC

• The average long term fuel trim weighted average value is greater or less than a calibrated value.
• The above condition is present for approximately 3 min after the Conditions for Running the DTC have been met.

Diagnostic Aids

• Allow the engine to reach operating temperature. With the engine running, observe the HO2S parameter with a scan tool. The HO2S value should vary from approximately 40 mV to approximately 900 mV, and respond to fueling changes.
• The normal Short Term Fuel Trim and Long Term Fuel Trim parameters should be between +10 and −10 % with 0 % the optimum, with the engine running at operating temperature.
• Any un-metered air into the engine causes this DTC to set. Thoroughly inspect all areas of the engine for vacuum leaks.
• A MAF sensor condition can cause this DTC without setting a MAF DTC. If there is a MAF sensor condition, the MAF sensor parameters will appear to be within range.
• Inspect the air filter for being the correct one for this application. Make sure that the engine oil fill cap is in place and that it is tight. Verify that the engine oil dip stick is fully seated.
• Certain aftermarket air filters may cause a DTC to set.
• Certain aftermarket air induction systems or modifications to the air induction system may cause a DTC to set.
• Certain aftermarket exhaust system components may cause a DTC to set.

Circuit/System Verification

1. Ignition ON.
2. Verify no other DTCs are set.
   • If any other DTCs are set
     Refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.
    
   • If no other DTCs are set
   
   
3. Verify DTC P0171, P0172, P0174, or P0175 is not set.
   • If a DTC is set
     Refer to Circuit/System Testing.
    
   • If no DTC is set
   
   
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed in the Freeze Frame/Failure Records data.
5. Verify DTC P0171, P0172, P0174, or P0175 is not set.
   • If any of the DTCs set
     Refer to Circuit/System Testing.
    
   • If none of the DTCs set
   
   
6. All OK.

Circuit/System Testing

1. Ignition ON.
2. Verify the MAP sensor pressure parameter is within the range specified for your altitude. Refer to Altitude Versus Barometric Pressure.
   • If not within the specified range
     Refer to DTC P0106.
    
   • If within the specified range
   
   
3. Engine running at the operating temperature.
4. Verify the Long Term Fuel Trim Bank 1 or 2 parameter is between −10 % and +10 %.
   • If greater than +10 %:
    
   1. Ignition OFF.
   2. Inspect for the conditions listed below:
      • Mass air flow sensor signal skewed—If the Short Term Fuel Trim parameters for both banks changes greater than 20 % when the MAF sensor is disconnected, refer to DTC P0101.
      • Contamination of the mass air flow sensor with oil or other foreign material.
      • Fuel contamination—Refer to Alcohol/Contaminants-in-Fuel Diagnosis.
      • Missing, restricted, or leaking exhaust components—Refer to Symptoms - Engine Exhaust.
      • Malfunctioning fuel injectors—Refer to Fuel Injector Diagnosis.
      • Vacuum hoses for splits, kinks, and improper connections.
      • Insufficient fuel in the tank.
      • Partial blockage of the air filter element or other conditions that alter air flow to the mass air flow sensor.
      • Low fuel pressure—Refer to Fuel System Diagnosis.
      • Vacuum leaks at the intake manifold, the throttle body, and the injector O-rings.
      • Leaks in the air induction system and the air intake ducts.
      • Missing air filter element.
      • Cracked EVAP canister.
      • Evaporative pipes obstructed or leaking.
      • The crankcase ventilation system for leaks—Refer to Crankcase Ventilation System Inspection/Diagnosis.
        • If a condition is found, repair as necessary.
        • If no condition is found, inspect the engine for a mechanical condition. Refer to Symptoms - Engine Mechanical.
        
        
        
      •  
    
   • If less than −10 %
    
   1. Ignition OFF.
   2. Inspect for the conditions listed below:
      • Mass air flow (MAF) sensor signal skewed—If the Short Term Fuel Trim parameters for both banks changes greater than 20 % when the MAF sensor is disconnected, refer to DTC P0101.
      • Contamination of the mass air flow sensor with oil or other foreign material.
      • Fuel contamination—Refer to Alcohol/Contaminants-in-Fuel Diagnosis.
      • Missing, restricted, or leaking exhaust components—Refer to Symptoms - Engine Exhaust.
      • Malfunctioning fuel injectors—Refer to Fuel Injector Diagnosis.
      • Collapsed or restricted air intake duct.
      • Excessive fuel pressure — Refer to Fuel System Diagnosis.
      • Dirty or restricted air filter.
      • Objects blocking the throttle body.
      • Improper operation of the evaporative emissions control system.
      • Excessive fuel in the crankcase—Change the engine oil as necessary.
        • If a condition is found, repair as necessary.
        • If no condition is found, inspect the engine for a mechanical condition. Refer to Symptoms - Engine Mechanical.
        
        
        
      •  
    
   • If between −10 % and +10 %
   
   
5. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed in the Freeze Frame/Failure Records data.
6. Verify DTC P0171, P0172, P0174, or P0175 is not set.
   • If any of the DTCs set
     Refer to conditions listed above.
    
   • If none of the DTCs set
   
   
7. All OK.

Repair Instructions

Perform the scan tool Fuel Trim Reset after completing the repair.

 

 

[asilverblazer]

Inspect for the conditions listed below:

12 hours ago, Chris Morris said:

It has codes stored but the light don't come on a lot and when it does they are gone in a few hours... I had a friend hook it up to his scanner and it showed the coolant temp and MAF sensor with faults on top of the P0172/175. So, I have replaced the plugs, wires, MAF, Coolant temp sensor, PCV Valve and have put seafoam in the gas tank. I have also cleaned the MAP/BARO Sensor... On another note there is a hint of gas smell on the oil dipstick...

 

SHRTFT1% (-19.5)

LONGFT1% (-35.2)

SHRTFT2% (-21.1)

LONGFT2% (-35.2)

FRP (47.4 psi)

• Mass air flow (MAF) sensor signal skewed—If the Short Term Fuel Trim parameters for both banks changes greater than 20 % when the MAF sensor is disconnected, refer to DTC P0101.
• Contamination of the mass air flow sensor with oil or other foreign material.
• Fuel contamination—Refer to Alcohol/Contaminants-in-Fuel Diagnosis.
• Missing, restricted, or leaking exhaust components—Refer to Symptoms - Engine Exhaust.
• Malfunctioning fuel injectors—Refer to Fuel Injector Diagnosis.
• Collapsed or restricted air intake duct.
• Excessive fuel pressure — Refer to Fuel System Diagnosis.
• Dirty or restricted air filter.
• Objects blocking the throttle body.
• Improper operation of the evaporative emissions control system.
• Excessive fuel in the crankcase—Change the engine oil as necessary.
  • If a condition is found, repair as necessary.
  • If no condition is found, inspect the engine for a mechanical condition. Refer to Symptoms - Engine Mechanical.

I'm curious what codes led you to replace the MAF? Some of the possible culprits could probably be ruled out if this is a long term problem. An aftermarket MAF sensor may not be acceptable quality. A thorough examination of the air intake track should be part of the diagnosis. 

 

Fuel injectors are also quite 'temperamental' and should be carefully considered/diagnosed, and replaced with OEM only. (Beware of counterfeit parts)

 

You also noted fuel smell in the oil, I seem to recall a faulty high pressure fuel pump can leak fuel into the crankcase. 

 

Some of the work performed so far probably didn't need to be and I wouldn't focus on in diagnostics: replaced the plugs, wires, PCV Valve, cleaned the MAP/BARO Sensor.

 

Other work might be making diagnosis more complex: MAF, Coolant temp sensor, seafoam in the gas tank.

 

Note the tests for the MAF above, a simple check of you aftermarket sensor.

 

I doubt the coolant temperature sensor is flawed - so long as you see reasonable temperatures on your scan tool.

 

I would make sure you run the gas tank as low as possible and refill to eliminate the seafoam as a potential "fuel contamination".

[rlcole321]

Wow, I didn't see O2B1S1, but if it is as high as O2B1S2 then you have a very rich condition (O2B2S1, S2 should be high, there downstream), and with the high negitive fuel trims, then there is something wrong, how long have you had the truck?, could the tank have been filled with E85?, what is the fuel rail PSI (high pressure)?

[Chris Morris]

4 hours ago, asilverblazer said:

Inspect for the conditions listed below:

• Mass air flow (MAF) sensor signal skewed—If the Short Term Fuel Trim parameters for both banks changes greater than 20 % when the MAF sensor is disconnected, refer to DTC P0101.
• Contamination of the mass air flow sensor with oil or other foreign material.
• Fuel contamination—Refer to Alcohol/Contaminants-in-Fuel Diagnosis.
• Missing, restricted, or leaking exhaust components—Refer to Symptoms - Engine Exhaust.
• Malfunctioning fuel injectors—Refer to Fuel Injector Diagnosis.
• Collapsed or restricted air intake duct.
• Excessive fuel pressure — Refer to Fuel System Diagnosis.
• Dirty or restricted air filter.
• Objects blocking the throttle body.
• Improper operation of the evaporative emissions control system.
• Excessive fuel in the crankcase—Change the engine oil as necessary.
  • If a condition is found, repair as necessary.
  • If no condition is found, inspect the engine for a mechanical condition. Refer to Symptoms - Engine Mechanical.

I'm curious what codes led you to replace the MAF? Some of the possible culprits could probably be ruled out if this is a long term problem. An aftermarket MAF sensor may not be acceptable quality. A thorough examination of the air intake track should be part of the diagnosis. 

 

Fuel injectors are also quite 'temperamental' and should be carefully considered/diagnosed, and replaced with OEM only. (Beware of counterfeit parts)

 

You also noted fuel smell in the oil, I seem to recall a faulty high pressure fuel pump can leak fuel into the crankcase. 

 

Some of the work performed so far probably didn't need to be and I wouldn't focus on in diagnostics: replaced the plugs, wires, PCV Valve, cleaned the MAP/BARO Sensor.

 

Other work might be making diagnosis more complex: MAF, Coolant temp sensor, seafoam in the gas tank.

 

Note the tests for the MAF above, a simple check of you aftermarket sensor.

 

I doubt the coolant temperature sensor is flawed - so long as you see reasonable temperatures on your scan tool.

 

I would make sure you run the gas tank as low as possible and refill to eliminate the seafoam as a potential "fuel contamination".

Thank you for all this info. There were no codes for the MAF but the other scanner showed a voltage error. I will run though all these tips tomorrow and see if I can find anything out.  

[Chris Morris]

1 hour ago, rlcole321 said:

Wow, I didn't see O2B1S1, but if it is as high as O2B1S2 then you have a very rich condition (O2B2S1, S2 should be high, there downstream), and with the high negitive fuel trims, then there is something wrong, how long have you had the truck?, could the tank have been filled with E85?, what is the fuel rail PSI (high pressure)?

The O2B1S1 was 0.110v. I must have skipped past it last night. The high pressure fuel rail at idle is 484.4psi. I have had her since birth and the station we use don't have E85 so it should be regular unleaded. 

[asilverblazer]

16 hours ago, Chris Morris said:

...and the station we use don't have E85 so it should be regular unleaded. 

If you always use the same station, you could have gotten bad gas - and keep putting more of it in. I've personally NEVER seen or know of anyone that has actually gotten contaminated fuel and consider to be an unlikely cause. 

 

Most likely problem(s) based on conversations here are injectors and/or high pressure pump.

[Chris Morris]

The MAF tested good. So I decided to just yank off the intake and ordered a injector tester. So when it gets here I will test them and if they are good I am going to put in a new High pressure fuel pump and cross my fingers. I might even just replace the pump and injectors.

 

[asilverblazer]

There is a scan tool function to test injectors... 

 

See this thread for injector balance test. Its a long read...

You'll notice how sensitive the injectors are.

 

I don't advocate changing parts unless you have a definitive diagnosis to do so, your opinion may vary.

[asilverblazer]

Quote

Fuel Injector Balance Test with Scan Tool

 

Note: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant.

 

Note: The engine speed must be between 600–1,000 RPM to perform this test.

Note: For engines with 2 banks of cylinders, only measure average pressure drop on cylinders that are on the same bank.

1. Ignition ON.
2. Command the Fuel Pump Enable ON with a scan tool.
3. Verify the fuel pressure is between 320–580 kPa (46–84 PSI) with the fuel pump running.
   • If not within 320–580 kPa (46–84 PSI)
     Refer to Fuel System Diagnosis.
    
   • If within 320–580 kPa (46–84 PSI)
4. Verify the fuel pressure does not decrease greater than 34 kPa (5 PSI) within 1 minute.
   • If greater than the specified value
     Refer to Fuel System Diagnosis.
    
   • If less than the specified value
5. Engine idling.
6. Verify the scan tool Fuel Rail Pressure Sensor 1 parameter is between 1.9–5.0 MPa (276–725 PSI).
   • If not between 1.9–5.0 MPa (276–725 PSI)
     Refer to Fuel System Diagnosis.
    
   • If between 1.9–5.0 MPa (276–725 PSI)
7. Select the Fuel Injector Balance function within the Control Functions menu of a scan tool.
8. Select and test a Q17 Fuel Injector. Repeat for each Q17 Fuel Injector.
9. Obtain and record a pressure drop value for each Q17 Fuel Injector.
10. Add all of the individual pressure drop values except for the fuel injector suspected of being faulty. This is the total pressure drop.
11. Divide the total pressure drop by the number of fuel injectors that were added together. This is the average pressure drop.
12. Multiply the average pressure drop by 0.20. This is the acceptable variance from the average pressure drop, 20%.
13. Verify the difference between any individual pressure drop and the average pressure drop is not greater than the acceptable variance.
    • If greater than the acceptable variance
      Replace the Q17 Fuel Injector.
     
    • If within the acceptable variance
14. Perform Fuel Injector Circuit Diagnosis.

 

[Chris Morris]

So I pulled out the injectors and tested them and cleaned them. They were good. With a rubber tip blow nozzle and a plug I tested the HPFP, and wouldn't you know it gas and bubbles coming out of the bottom piston seal. Getting one ordered with new O-ring kit for injectors and intake gaskets. I will post once work is done. Fingers crossed I will be good.