Rick's Free Auto Repair Advice

Stalls but restarts

Stalls but restarts after cooldown, GM truck

If you own a late model Avalance, Silverado, Suburban, Sierra, Denali, or Yukon and experience a problem where the vehicle drives and then just stalls out as if it has run out of gas, well, it has (kinda). This problem can also set a P0230 or U0109 trouble code, and can also show up as a no start after stall.

Shops are reporting problems with the fuel pump control module (FPCM), not the pump itself. Here’s how it works. Rather than run the electric fuel pump at full speed all the time, GM designed a regulator of sorts. The PCM looks at the throttle position sensor, MAF sensor, speedometer, etc. to determine how much fuel to deliver. Then it sends a digital signal to the FPCM to adjust driving voltage to the pump. So, if you can the accelerator, the FPCM commands full pump output.

The most common problems with the FPCM are high resistance and poor ground connections. Start by verifying power to the FPCM. Then, with the key off, check the resistance at the diagnostic link connector between pins 6 and 14. The reading should be about 60-ohms. Next, check the ground for the FPCM. In reality, you should check the condition of the ground while commanding the pump on with a scan tool. Since you probably don’t own a $2,500 scan tool, just assume the ground connection is bad and clean it. Also clean the body to frame ground strap, especially if the problem seems to be ambient temperature heat related. Then apply dielectric grease to the bare metal and reassemble the ground. If the problem goes away, you’ve saved yourself a lot of money.

If that doesn’t fix the problem, you’re probably looking at a new FPCM. In worst case, you’re looking at a new fuel pump

 

© 2012 Rick Muscoplat

Posted on by Rick Muscoplat


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