Chevy Sonic engine shutting down

Hey. My 2012 Chevy Sonic 1.8L AT shut everything down 2 days ago. After rolling into a parking lot and sitting for ten minutes the vehicle started like it should. Now it shuts everything down when the engine is cold and I have to wait to restart then its fine for a short drive.

Battery is good, alternator is in the process of being replaced. Battery current sensor replaced. Keyfob battery replaced. I am gonna replace the Crankshaft sensor and install the new alternator tomorrow.

BTW after it shuts down I still have dash lighting and radio just the engine won’t turn over. If anyone has any idea something I haven’t thought of…

Something I forgot to add… There was an intermittant squealing in the engine bay that I thought was the A/C compressor for a week before this all started to happen.

What does that mean?

You turn the ignition switch to start, and nothing happens?

Or, the engine turns over, but the engine doesn’t fire(run)?


Is it posting any diagnostic codes? When the engine is running, is the check engine light on?

This sort of sounds like a security or computer module interconnection problem at first glance.

Ummm… Is this a bot?

Tester isn’t a bot. A real person, and very experienced in auto mechanics.


Hey. No diagnostic codes whatsoever. I am leaning towards the voltage regulator in the alternator going bad or the crankshaft sensor. There is a module: Body Control_ that turns the alternator on and off but I topped off the battery today so the alternator is still charging it a little at least.

Measure the battery voltage. It should be about 12.6 volts before first start of the day. Immediately after starting the engine, 13 - 15.5 volts.

Here is where it gets weird…

The battery is measuring 12.9v with the car off.

After turning the car on the voltage goes up to 14v like it should but it doesn’t stay there. It goes down to 12v after a minute or so at idle no load. Then when I add headlamp nothing changes. That is why I am replacing the alternator.

Those voltages seem ok. I doubt you have an alternator problem. 12.9 v in the morning after the car has been sitting unused all night is a little high. I expect that’s not the case however, and when you read 12.9 v the car was recently been running a little at least. It’s normal for newer cars with their sophisticated charging system to start charging at higher voltages, then realize it isn’t necessary and drop it down. It’s a little surprising it would drop below 12.6 volts though. That’s sort of the nominal fully charged battery voltage at normal temperatures.

1 Like

you should change your belt, tensioner and pulleys too. that’s probably your squeal. if its slipping its not charging properly.


That could be the serpentine belt slipping on the alternator pully because the alternator is on the way out.


Check the voltage. A good car battery should read 12.4-12.9 volts when the car is off. Anything lower doesn’t necessarily mean the battery is bad. Your car’s electrical system may have drained it, or there may be an issue with your alternator. Recharge the battery and test it again later to see if it’s holding a charge.


1 Like

Hey. Great advice. I will check the tensioner when I replace the alternator tomorrow. Thanks. I checked the v-belt. It looked ok however I still don’t know what that squealing is and I haven’t been able to replicate it. It sounded like a bad steering pump but the Sonic doesn’t have that type of power steering.

Hey. That was my theory and these recent electrical issues made me believe that the alternator was the squeal and it needs to be replaced. Car isn’t overheating, and A/C works and transmission is fine.