P0641!!

[elamigowapo]

My truck a 2008 silverado 5.3 is throwing a p0641 and p0107 code the second being the map sensor. The truck was at the shop for a few days and my mechanic states that the truck needs an ecm. He said he was able to verify that allof the sensors on this circuit are functioning well. Im hesitant to buy an ecm however can you always see that sensors are working through a scanner. What if it is just a sensor? He also showed me thay all of the sensors on the circuit were only running on 2 volts.

[e_schott]

The P0641 is from the 5v reference voltage being pulled down, the 5v ref goes to many different sensors on the engine. Possible that it could be the PCM, but also possible that one of the sensors could have high resistance or a short pulling the voltage down lower, or there could be an issue with the wiring somewhere in the harness. What I like to do is monitor the 5v ref with a dvom and unplug the sensors on the 5v ref circuit one by one to rule out each sensor. If at the start of this test the 5v ref line is at 2 volts, and unplugging one of the sensors brings the voltage back up to near 5, you know that sensor is an issue. If you are not comfortable doing the test, I would get a second opinion from another competent technician before you condemn the ECM.

[e_schott]

Was racking my brain on this and I am not 100% sure if it was a silverado of this vintage or not but I remember at some point years ago I had this code on a silverado that came through the door and it ended up being a fuel tank pressure sensor. Not saying that is your issue just trying to re-iterate that there are a lot of things that can cause that code.