Hello everyone,

I have a 2009 Chevy Cobalt LNF Sedan Manual,

Recently I drove through a pretty deep puddle on the way home. Left car overnight and it was dead the next time I tried to turn it on.

So I ended up charging the battery again and as soon as I hook up the positive & negative cables the car starts cranking. I've ruled out the possibility of it being the starter by bench testing it.

The last thing I noticed with my multimeter was I was getting power (12v) to the starter solenoid before the key was even in the ignition.

Does anyone have any idea where i should look next? I was thinking of checking for corrosion in the wiring harness, but I don't have a diagram.

 

Check the starter relay... just swap in another one that's less important and see if that cures the issue.

I've had that issue with the fuel pump relay before. Very well might not have even had anything to do with the puddle... just bad timing.

If that doesn't fix it... you're in for a "fun" time, most likely.

 

Yea I tried that. Unfortunately same issue where I'm still getting voltage to the starter solenoid before the key is in the ignition.

Guess I have to start prepping for this fun time!

 

Could be the starter solenoid itself has a short in it.

 

I've ruled out the starter since I've pull the starter completely off the car and there is still ignition voltage going to the plug that connects to the starter.

IE the one pictured below. (Yellow line, and not my picture just pulled random picture online for example)




So it acts like someone is permanently turning the key while the battery is hooked up.

Does anyone have a wiring schematic that relates to that connector?

 

see if this helps

 

 

Thanks Jared! Appreciate it. Now I just have to learn how to read this.

 

Yeah, i haven't the slightest how to read schematics either. I generally stay clear of electronics, we've had our disagreements in the past, lol.
But what I would do is go from the starter, and work backwards checking relays and fuses.

 

Welp, I might have found the issue, looks like water someone got into the ECM connector?

Left connector vs right connector, seems like the left ones completely fine. The right one however might not be recoverable since some of the pins were corroded and got obliterated it looks like.

Does anyone know if I would be able to find swap an ECM in from another LNF cobalt I could potentially find in the junkyard? or should I just get this ZZP ECM

 

Im guessing the ECM/PCM are the same component on this car? 2009 Cobalt SS 2.0 LNF Sedan

 

Yikes. That would probably do a bunch of weird things.

 

Woof, that's bad. How deep was the water you drove through???

ECM and PCM are the same component on this car. There's a BCM that's under the radio. Both PCM and BCM are VIN locked. I would just jump to something like the ZZP PCM.

 

It was actually not that big of a puddle, probably up to the center of the wheel.
I'm thinking since I didn't have the inner wheel liners installed the water got kicked up. That combined with the PCM connector seal being bad, water got in.

Cleaning the PCM pins and the connector itself with some electrical cleaner and a brush seemed to solve my issues (for now). And I was no longer getting voltage to the starter UNTIL depressed the clutch & turned the key, perfect.

I was able to clean the pins off, but a couple of them just fell off from the corrosion. I also opened up the PCM to check for any obvious damage and there was none.



Looking at some pin diagrams I found online the pins didn't seem critical to get the car started again. However I would like to have everything functioning properly again.
I'd rather not get another PCM and pay the cost to get it reprogrammed with my VIN (I believe that's how it works) .




So I was thinking while I have the PCM open I can solder some cables directly onto the PCB where the pins would have connected too if they weren't broken anymore. and have them just come out of the side of the PCM , and splice them back into the wiring harness.
Not the cleanest solution. But most definitely the cheapest.

 

I would look into getting a PIN repair kit. Splicing everything like that sounds like a bad idea that if/when you try to reverse it has the chance of causing more issues.

 

Totally ended up working, sealed up the ECU and the now the car is running flawlessly. Now to decide which mods to do next.

 

Good to hear. I just remembered that I have a 42k miles LNF engine harness in my garage, if you would have needed it, as well.

 

According to problem with missing pins. I will go to use these ones "not used". Solder in ECU from missing to "not used" and change it in cable connector. But be careful diagram can be (a little) wrong. When modding in BCM best option was to chceck with multimeter. Got three diagrams that was theoretically to my car and only one was closest to true. Probably you will got no cable in connector from "not used".