P0641

[08H3]

Looking at a 2008 H3 that is in great shape other than an intermittent DTC P0641. Anyone have any experience with this issue? I know it's a general code with something wrong on the 5V rail. Is there a most likely culprit or would this end up being an electrical gremlin I would never be able to sort out? Thanks in advance for any input.

 

[Jeepwalker]

Does it just set a 'soft' code? (not go into closed loop?).

It could be as simple as corroded battery terminals, but more than likely it's a bad or corroded pin/connector/ground, ..rodent-chewed wire, etc. If you live in an area where things rust or corrode from road or moisture elements, that could well be it. Probably take some old-school sleuthing and physical inspection of the components to track it down. What's your skill level/experience in tracking down electrical issues?

 

[08H3]

Assuming we are both defining soft code as one that doesn't come right back when cleared, then yes. I did not experience the code or any issues when I test drove it. It ran flawlessly. I am only going by what the current owner is telling me. Seems like a really stand up guy who is making sure I know everything upfront. He could have never mentioned it and I would never have known, so I get a good feeling from him. He said it happened twice over the past 2 weeks seemingly at random and did clear itself. I am in the rust belt, but honestly I've never really had issues with GM connectors even in the most extreme environments. They seem to seal well in general. Rodents, abrasion definitely possible.

I guess I would say Im decent in tracking down electrical issues, but that doesn't mean I enjoy it by any stretch.

 

[Jeepwalker]

The stock battery connections were problematic for a lot of guys. And poor battery connections on any 'modern' vehicle are a source of whacky electrical issues ...including door module problems. It could be as simple as that. And there could be corroded grounds. They'd be easy to inspect and re-seat.

When I took the interior and carpet out of my H3 a couple years ago, there are grounds all over the place ya never see ...and some of them were corroded pretty bad (from prior water leaks). Now, I wasn't experiencing any electrical problems, but that's an example of the kind of thing a guy 'could' run into. And connector pins can/do corrode from time to time. Some of the engine's sensor wire's in the H3 have been known to vibrate and rub through the plastic coating. So there are several possibilities that could cause it, but to my mind, none are that difficult or would stop me from buying it ...if it's in good shape/priced right. Chances are there'll be many other things you'll have to do/repair if you do buy it. Good luck!!

 

[08H3]

Thought I would update my own thread in case someone searches for the same thing in the future. Ended up the wire to the camshaft position sensor had rubbed against the valve cover and shorted to ground. It had to be one of the following sensors; MAP, camshaft position, oil pressure , ac pressure , accelerator position , fuel tank pressure , or the wiring somewhere in between there and the PCM. I took a gamble buying it figuring that nothing would be an expensive repair. Just a potential for a lot of time and frustration trying to find it. Got really lucky that it was probably the easiest area to find and repair. I think the plastic wire loom is a terrible product. Not just on the H3, but just a junk product in general that should not be used in any automotive application. Any time I have to replace it, I use silicone vaccum line. It's heat resistant, abrasion resistant and will last the life of the car unlike the plastic garbage. I taped it all the way up on this repair just because what I had on hand was ugly orange. Also found 2 other bare wires in the process of tracking this down. On my first Hummer, I had a misfire caused by a fuel injector wire being rubbed bare under the intake. This one had the secondary air injection wires rubbed bare under the intake. I think as preventive measure you sould either find an AirDoc or add the silicone tubing around everything under the air intake. As another tip for tracking down similar wire issues, I would recommend looking for shiny spots on the metal where it's been rubbing. The spot on the wire was so small it was almost unseeable, however the shiny spot on the valve cover was much larger and more noticeable.

For posterity sake and anyone coming across this thread in the future, mine would only throw the code under hard acceleration. That led me to believe it was most likely the APP sensor or a bare wire that was being pushed against ground due to motor twist. Also, the sensors I listed apply only to 2008. The wiring on 2006 and 2007 are different. Not sure on 2009 and 2010, but I know for sure it's a different set of sensors on that 5V rail on earlier models.