Chevy Cavalier OBD code p0621...what?

Question

My mom's 2003 Chevy Cavalier threw a battery light and I'm trying to track down if I can fix it or not. I'm very confused by the code though:

Car starts and runs fine
I have a cig lighter tester for starter, alternator, battery. All checked out
Battery Light comes on after about 10 minutes
I got a p0621 code from my OBD
The alternator circuit on my cig lighter tester was destroyed.
The car battery started discharging.

I shut the car off, turned it back on after 3 minutes and the battery light was still on.
I drove it home roughly 30 miles on a highway without issue. When I got to a stoplight things went pear shaped.
I kept going after waiting at the stoplight, car was driving ok.
At the stoplight my OBD computer lost connection with the car and I couldn't re-establish.
The Transmission lost it's ability to change gears, I believe it stuck in 1st.

Does anyone know where I can start to diagnose this? The alternator is under an engine component, but the wire harness was connected and didn't look to be in bad shape.

I found an ACDelco link saying to check the horn fuse.

Any other ideas? I have no idea what would allow the car to run fine until I reach the stoplight, and then apparantly have the computer go offline but allow the car to run.

These are the same symptoms my mom had yesterday, and the go away with the car being left long enough.

Anonymous · Accepted Answer

FYI - you cannot check the vehicles diagnostics through the cigarette lighter

its the alternator, battery, or a bad connection in between (assuming there are no fusible links) - the alternator charges the battery while the components of the engine run from the battery (depending on the make) I can tell from what you said about the trans. Since you have lost power to the trans electronic shift module, the trans will not shift. Simple tests:
1.) Start the vehicle (may need to jump it) pull of the negative battery terminal, if it dies its the alternator
2.) start the vehicle (may need to jump it) use a  voltmeter to check DC power on each battery post should read between 12.7V and 14.5V if not- its the alternator
3.) after you have started and run the vehicle for approx 10mins. shut the car off and check the battery with a voltmeter if you have less than 12V DC you may have a bad battery

of course you can take all these items to your local autozone where they test them for free - hope you dont have a slipping serpentine belt

bastick · Answer

while you're in any respect promptly prone, it is common to replace a thermostat. All you prefer are some uncomplicated kit a clean thermostat and gasket. you may additionally prefer some greater beneficial coolant in case you lose too plenty once you eliminate the impressive radiator hose.

? · Answer

horn fuse?   for not running right?  lmao.  take it to someone who knows something about cars

Anonymous · Answer

take it to autozone, advance auto, o'riely's and have someone with the proper equipment to test your battery/charging system.

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Chevy Cavalier OBD code p0621...what?

4 Answers