No start when hot 2007 Pontiac G6 3.5L

[Boomer]

Will do. Certainly open to more suggestions from everyone. and what area would be likely to check thoroughly? I don’t have a manual on this vehicle.

 

[billr]

"One weird thing that I noticed. It would be running ok and then you drop it in reverse and it would die sometimes right away..."

That is also a hint to look for a cracked vacuum hose. When put in reverse, the whole engine/trans assembly is torqued in the opposite direction from normal, so can flex hoses different than "normal" and open cracks that are mostly closed when not in R.

 

[Boomer]

"One weird thing that I noticed. It would be running ok and then you drop it in reverse and it would die sometimes right away..."

That is also a hint to look for a cracked vacuum hose. When put in reverse, the whole engine/trans assembly is torqued in the opposite direction from normal, so can flex hoses different than "normal" and open cracks that are mostly closed when not in R.

Thank you, Bill. In a car this old, I can see dry rotting hoses being a thing. I'll give them a visual inspection. I know some of the wiring around the engine is exposed. The factory flex loom is so brittle that it crumbled when I touched it. I'm going to pick up some new loom and get all of that covered when all is said and done.

 

[grcauto]

Thank you, Bill. In a car this old, I can see dry rotting hoses being a thing. I'll give them a visual inspection. I know some of the wiring around the engine is exposed. The factory flex loom is so brittle that it crumbled when I touched it. I'm going to pick up some new loom and get all of that covered when all is said and done.

Much more likely it's electrical rather than loss of vacuum. That would be a massive opening to stall the engine. Your wiring needs attention.

 

[billr]

I have seen some seemingly "non massive" vacuum leaks cause severe problems, but agree electrical is more likely since there is also a problem starting. When starting, the MAP is near-atmospheric, so a vacuum leak then is almost irrelevant.

 

[Boomer]

Much more likely it's electrical rather than loss of vacuum. That would be a massive opening to stall the engine. Your wiring needs attention.

Any certain location this wiring may be?

 

[grcauto]

MAN. Just start it and let it idle while you go around and tug on the wiring harnesses. Takes all of a few minutes.

 

[Boomer]

Doing just that. So far, no issues. It's running fine in all positions. Just sent her out for a short test drive to see if we can get the problems to come back. We did clear one code. The C0561 Invalid serial data. Related to ABS. Didn't cause any problems though like I said. So far it's running fine.

 

[Boomer]

Well, after all of the inspections you guys have recommended, the car didn't exhibit any of the problems. It's running fine. Even in reverse. Kind of hard to fix a problem that doesn't seem to be there. We shall see if they return. We did disconnect the negative battery cable for awhile thinking maybe it would give the ecm a hard reset. I find it hard to imagine that would fix it.

 

[billr]

Well, disconnecting the negative battery cable certainly "wiggled" that wire, and "reset" its connection to the battery.

 

[Boomer]

Well, disconnecting the negative battery cable certainly "wiggled" that wire, and "reset" its connection to the battery.

I couldn't find anything amiss with the wiring. I do see that the brake lights are stuck on as long as the key is on. I'll have to see if I can find a wiring diagram for that.

 

[nickb2]

Hey boomer, long time no speak.

I found this TSB which seems to apply.

I also included whole wiring for the car. notice where the ground G302 is. Try cleaning that first. It says under left rear seat back. Page 2 of four.

 

[nickb2]

I have been real busy lately, so late to game often, but I will try to help.

I remember once having an issue like this with a client car. some kind of buick type deal. It ended up being the fuel pump circuit would get hot in the PDC front engine bay. Causing all kinds of codes as you describe.



I used a flir gun to check, that helped. I ended up replacing the whole PDC. All grounds and what not where perfect, once I ohm the actual PDC itself, fuse side to connector side, mucho resistance in the PDC itself.

Some rebuild these, look for bargain there, you may get a core value if in fact it is the PDC itself.

But FIRST and foremost, you gotta get all those grounds cleaned up first. GM is NOTORIOUS for bad grounds.

 

[nickb2]

If you can get your hands on a power probe four, I f ing love this thing.

Great investment if you work on cars regularly.

It has a resistance option with live feed. Absolutely great just for things such as this.

Also, as grc noted, wiggle testing is good, but if that is no go, look for restrictive grounds. Or choke points as we say in the industry.

Here is a short video of what a power probe 4 is and how this cheap thing can be of value. And NO, I dont endorse this company, I just like the tool cuz it actually does what it says it does and is very robust. Worth every penny I spent in my mind.

 

[nickb2]

So if you took the time to make it to the end of alberta guy video, the feed test option is what I love the most for problems such as your (I think daughter ride)

I catch alot of problems my regular multi meter wont cath, cuz this one actually gives me a reading on voltage drop in a circuit and I can also read ohms at same time. This it where it shines.

That is how I found that buick problem, which had exact same symptoms and problems as this g6. In my opinion, g6 and buick of same era, those PDC's sucked large, much like mopar ones.

Anyway, nuff talk, try ebay or similar for the probe 4. The hook is out now, but WAY to costly to justify an investment yet as I have all kinds of other shyte to work with, but man, do I love my probe 4 for things such as this thread.