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Kelle

Chasing a P1174 code in my 6.0l

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Hey guys. I've been chasing a p1174 code (fuel trim cylinder balance bank 1) in my 2008 vortec max 6.0l for awhile now. It's a non-flex fuel with afm. It's not throwing any other codes besides that one. Has a slightly rough idle but starts and drives great. Looking at the live data, all of my o2 sensors appear to be normal. I noticed my long term fuel trims on both banks sit around 0-5% at idle but jump to between 14-25% while driving so something is definitely telling the PCM to add fuel. I checked my fuel pressure and with key on engine off I get right around 60psi. Strange thing is it only has around 44psi at idle and while driving. Even stranger was when i unplugged the MAF sensor, my fuel pressure at idle went up to 58psi and stayed there. When I shut the truck off the pressure climbs to over 70psi and holds for some time. Also unplugging the MAF sensor also caused the "service stabilitrac" message to come on which made me scratch my head a little. Checked the intake for vacuum leaks and found nothing. Has anyone dealt with this code before? Really hard to know where to start with such a vague code and I dont understand why unplugging the MAF sensor would cause the fuel pressure to rise 14psi. Any help is appreciated. Thanks in advance!

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- Check other vacuum like brake and pvc
- check if still in Open loop. In open, system would feed more fuel assuming the vehicle is still cold
- those fuel pressures are normal. Pressure should rise at higher rpm. Disconnecting the MAF might set you back into open loop requiring more fuel and thus have the ecu increase fuel pressure
- check other sensor inputs (air temp, water temp, tps etc)

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23 hours ago, Kelle said:

Hey guys. I've been chasing a p1174 code (fuel trim cylinder balance bank 1) in my 2008 vortec max 6.0l for awhile now. It's a non-flex fuel with afm. It's not throwing any other codes besides that one. Has a slightly rough idle but starts and drives great. Looking at the live data, all of my o2 sensors appear to be normal. I noticed my long term fuel trims on both banks sit around 0-5% at idle but jump to between 14-25% while driving so something is definitely telling the PCM to add fuel. I checked my fuel pressure and with key on engine off I get right around 60psi. Strange thing is it only has around 44psi at idle and while driving. Even stranger was when i unplugged the MAF sensor, my fuel pressure at idle went up to 58psi and stayed there. When I shut the truck off the pressure climbs to over 70psi and holds for some time. Also unplugging the MAF sensor also caused the "service stabilitrac" message to come on which made me scratch my head a little. Checked the intake for vacuum leaks and found nothing. Has anyone dealt with this code before? Really hard to know where to start with such a vague code and I dont understand why unplugging the MAF sensor would cause the fuel pressure to rise 14psi. Any help is appreciated. Thanks in advance!

Ok well I have some good news for you. Going to do some explaining on your post before giving you the answer lol.

 

60 PSI of standing fuel pressure (key on engine off) is good fuel pressure. The reason your fuel pressure drops is because of 2 reasons. 1.) The regulator in the fuel tank (which is completely normal) 2.) The FPCM commands it to that. The reason it creeps up is the same as #1. Pressure in the tank from the EVAP system sealing causes regulator pressure differences.

 

The reason why when you unplug the MAF sensor the Service Stabilitrac light comes on is because it is giving you a generic  C0561 System Disabled information stored code from when the PCM is detecting a problem. Perfectly normal condition.

 

While you unplug the MAF sensor the reason the fuel pressure goes up is because the FPCM goes to default and it commands the pump pressure to 100%

 

Now, You're exactly right when you say it's really hard to know where to start and when you start doing random testing and unplugging stuff, you're going to start causing all kinds of self inflicted conditions and make yourself guess at what's the problem when there is really nothing wrong other than the problems you created. lol

 

Now for the fix. I have run into this multiple times, and there is actually a bulletin from GM on this. The Max was terrible for this code.

 

The ECM Calibration is the failure. I don't know why out of the blue it causes it. But it does. 

 

#08-06-04-028: Service Engine Soon/Malfunction Indicator Lamp, DTC P1174 Fuel Trim Cylinder Balance Bank 1 (Reprogram ECM) - (Apr 28, 2008)

 

Condition

Some customers may comment that the Service Engine Soon (SES)/Malfunction Indicator Lamp (MIL) is illuminated. Technicians may find Diagnostic Trouble Code (DTC) P1174 Fuel Trim Cylinder Balance Bank 1 set.

 

Cause

This condition may be caused by calibration sensitivity.

 

 

Correction

 

Do - Update the ECM calibration.

Do Not - replace the catalytic converter, ECM, injectors, fuel rails or fuel pumps.

 

Go to your local dealership and have them update the PCM calibration and you will be back to new in no time. Make sure you quote me in a reply so I know that there is a reply. I post so much sometimes I overlook a reply. But I will not overlook it if I am quoted. Hope this helps. Let me know if you need anything else!

 

  

 

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