Intermittent electrical problem, sometimes prevents 2006 Chevy Cobalt from starting

I have had an occasional electrical problem with my Chevy Cobalt for a year or two. It seems to come and go (no issue for weeks, then it will occur most days over the course of a couple of weeks).

While driving, the dash will go dead (the gauges go to zeroes, the LED display with the miles and temperature goes blank or dashes), and the radio will go dead. I can still drive the car, and I have HVAC. The turn signals work (i.e., the lights blink), but I don’t hear the distinctive ‘turn signal clicking’ sound. Worrisome and annoying, but the car still runs.

Where it is a real problem is, if it happens when the car is off the car won’t start. I turn the key, and there is nothing. No ‘clicking’ of the starter, nothing. Typically I wait, try starting the car again 10-15 seconds later, and eventually I can start it within 5 minutes.

Anytime this happens while driving, it won’t last long. The dash / radio will go out, and then come back in a minute or two. It might happen a second or third or fourth time, but never for long.

I asked a dealer about it last year, when I was visiting for something else. They told me they could look, but since it was intermittent they probably wouldn’t be able to reproduce it, and may not find anything, and I would just be paying $90 / hour for labor to not find anything. They took a quick look under the hood and did find and clean out what appeared to be the remnants of a rodent’s nest. (the car never goes more than 3-4 days not driven, so the nest couldn’t have been active long, I don’t think.)

Anyway, my best guess is a bad connection or control module somewhere, possibly caused by a rodent gnawing on something. There is no pattern to when it happens (dampness, temperature, time of day, etc.) I don’t know the electrical system of a Cobalt to try and trace down the potential problem location.

Has anyone seen something similar before in a Cobalt?

You provide some pretty good clues to help locate the what section of the power distribution system the trouble is in. Looking at some data for your vehicle it shows there is a fuse in fuse the panel under the hood called the S-band OnStar fuse that powers the digital radio and Vehicle Communication Interface Module (VCIM) tied to pin connection F5 of the fuse block. I suggest you check the power at that point when the trouble happens. The more things you can find that don’t work while the trouble is occurring the easier it will be to locate the problem section of the power distribution system. It may be a wise investment to get a factory service manual that covers the wiring for the vehicle to help you pin down the problem area. Ebay is a good place to purchase service data.

Thank you for the information and suggestions. It is so intermittent, I’ve never had time to diagnose anything. But if I can get my hands on a good schematic or wiring diagram, I could probably narrow it down a bit.

Ebay is a good place to get the factory manuals for vehicles. Be sure to get the a factory version since they provide the best details of the wiring. You might also be able to get some info through your local library.

I think you’ve probably already diagnosed it correctly. A bad connection going to the dash area, likely due to rodent damage. I’d guess it is a power or ground problem, not just one of the signal wires. If I had this problem I’d use a schematic to find all the connectors that involve these functions and check them one by one for corrosions or damage to the wiring harness. If that didn’t work I’d connect a voltmeter to the power lines and monitor that voltage over the course of driving the vehicle. Eventually I’d hope to see a voltage drop-out that correlates with the symptom.

Before you do anything difficult or expensive try this: There are two ring lug ground connections at the front of the bell housing, at least there are on my manual trans 09 Cobalt. Clean these to see if it will help. I had a strange electrical problem, not exactly like yours but similar with a mid 90s Cavalier. Cleaning the described ground connections took care of it. My Cobalt has the ground connections at the same location as the Cavalier.

Just to add to what @Wha Who stated. One easy way to see if there is a grounding problem is to install a temporary jumper lead between the suspected bad ground area and a known good ground point.

Has your car had the ignition switch recall done?

Thank you everyone for the advice.

I have had the ignition switch recall done. The problem started before that, and it didn’t seem to affect things better or worse.

Between the library and a family member at Delphi, I’m digging up schematics for my car. That should help find some potential problem locations.

Here’s a dash schematics. The next time it does not start, turn the key to run for a few seconds, then to off and back to run. Then try to start it. If it starts it probably the fuel pump. If not, probably the starter.

Looking at the schematics they show the cluster fuse is provided power from the power distribution system. Since the radio is having touble also when the problem happens I would guess that the problem is somewhere before the cluster fuse and where the power also ties to the audio system.