P0641 code?

[tlsnokuyeulb]

As I was driving today, most of the day was good. Then as I was turning a corner, the yukon just died. I get all the dic messages, but borrowing a code reader yielded P0641. According to the autozone print out I should replace the fuel pump control module. Does this sound credible? I currently don't have the resources to just throw parts at it right now. Actually, I drive for Lyft and was on my way to pick up a passenger and this happened. Ironically I'm also chasing down a squeak which I suspected a u joint but apparently I replaced the wrong one or I'm looking in the wrong place. What do you all think? I need this thing back on the road ASAP! Thanks!

 

[1_8TTony]

I don't see the year of your vehicle listed.....so I am going to just generalize a little here......

There is a recall for this part. Call your local dealer, give them your trucks VIN identification and let them check GM's records to see if the part has been replaced yet. It will be a free repair if it has not been replaced yet.

The fuel pump in newer model Chevy trucks have a variable rate of flow. The fuel pump control module regulates the amount of voltage sent to the fuel pump. Higher engine rpm's cause more voltage to be sent to the pump. Lower engine rpm's cause less voltage to be sent to the pump. Basically: Fuel flow is dependent on the amount of voltage the pump receives.........voltage is dependent upon engine rpm's.

Ok so, knowing this, the first logical thing to do is check the fuse associated with that fuel pump control module. Next, check the fuel pump voltage on the fuel pumps voltage input wire.

Orange/Black wire is the fuel level sensor reference wire
Purple wire is the fuel level sensor signal wire.
GREY IS THE FUEL PUMP POWER WIRE
Black is fuel pump ground

^^^^^ Those are the colors of the wires that operate the fuel pump module. The other wires not described monitor the FTP sensor.

Use a volt meter and see how many volts are on the grey wire at the end of the fuel pump wire harness. If you don't have power and the pump wont run, you probably have a bad control module. If you have no power but can "hotwire" the pump and the pump runs, you probably have a bad control module.

 

[tlsnokuyeulb]

Thanks 1_8TTony. I have an 07 4wd. I found the problem though. It appears that the front driveshaft was cutting into the loom right above it and exposed the gray wire, which you stated was the fuel pump power wire. I taped it up, taped the loom and zip tied it away from the driveshaft and so far no more issues. Weirdly enough, that seemed to have solved my squeak. My guess is that the loom and the exposed wire were sending some vibration through the shaft causing the noise. I found this: http://sparkys-answers.com/2015/08/2008-gmc-yukon-reduced-power-mode-code-p0641-00-stored.html searching another thread. I hope this has solved my issue. Also, the recall wouldn't have mattered to me because I had replaced the fuel pump already.

 

[1_8TTony]

Also, the recall wouldn't have mattered to me because I had replaced the fuel pump already.

I was talking about the TSB recall in regards to the fuel pump control module, not the actual fuel pump.

Good to hear you got your truck running again.