Electrical/Driveability Issues

[raygussy]

Hello All, 2008 Avalanche, 145,000, 5.3. I'm getting the dreaded GM symptoms. Check engine light, (Code P0641 Sensor Reference Voltage 'A' Circuit Open) Reduced engine power, Service Stabilitrak, Traction Control, Oil pressure bouncing around, you know, the usual...

Thinking about trying a new pcm, but I want to share everything I've already tried without any luck. This issue has been intermittent until yesterday. In the past I would disconnect the battery and the next day it would start and run fine, but not today. It started and ran fine for about 2 miles then I got the issues listed above.

Within the last six months:

Plugs, wires, coils
Battery
Cleaned all engine/chassis grounds, added another engine ground
Cleaned 150 amp fuse on firewall and battery clamps
Ignition switch (two, in fact)

Any ideas? Worth trying a new pcm?

Thanks!!!

 

[raygussy]

Sorry, also replaced TPS and Oil pressure sensor...

 

[BainMan]

Does this help? See attached

 

[raygussy]

Thanks. Unfortunately it sounds like a p0641 with my symptoms can be caused by a lot of different things. I'm not sure if this could cause what's happening, but I just ran my scan tool and found out the alternators putting out 15.6 volts, which is at least one volt over what it should be putting out. The problem is I don't know if that condition could cause what's happening. Thanks again

 

[Wpolonavyguy]

My Avalanche is getting rediclieously close to new as troubleshooting my intermittent issues.
There were some legitimate fixes needed & some I found by dumb luck & reading posts in these forums.
The computer system in mine was acting up recently I cleaned all grounding points I could & added additional. I even bought cable & used extra battery tray to have double battery life with a junkyard salvaged main fuse between just precaution. Culprit I found was negative post on battery was slightly smaller than the terminal could grasp tightly, I could spin it even with bolt as tight as it would go.
I ordered aftermarket terminal with better clamping mechanism most electrical symptoms improved.
These consume oil through the pcv system, mine changed drivers head gasket & have catch cans both sides pcv vacuum lines.
I cleaned goop when removed intake manifold could see oil tracks through all fuel/air ports.
These are difficult to diagnose without having mecanic grade odb2 scanner, my basic 50$ harbor freight one I chased many ghost problems and shot parts cannons.
Good luck