90 grand prix code 15, 43,53

I will look them up on the web for you:

15 colder than -38F 43 Knock sensor 53 battery more than 17.1 volts

After doing a primary electrical check for voltage and drops, and verifying they were good, I reset the codes, took it for a test drive. Ran great all the way to the store. I shut it off and left it for 30 minutes in the 15 degree air. Immediately after i fired it back up, it stumbled and died and check engine light came on. (code 53 - over voltage 17.1 for 2 seconds or longer.) I spent about 5 minutes trying to restart it. When I did, it ran somewhat rougher than it did prior to stalling but it never stalled again for the 15 minute drive back from the store. The only thing to cause over voltage (over 17.1 volts,) would be the alternator. More specifically the regulator, so am opting to R and R it.

It could also be the ecu is going bad and it just thinks it was over 17.1 v. Check the grounds on the ecu. It could also be an intermittant connection to the alternator.

Put new alternator in for no other reason than the computer sensed it was putting 17.1 volts for more than 2 seconds. After driving for a few miles, it stalled once again. Immediatley checked code ; turned out to be 53 again. After bench testing at the local auto parts store, and doing an in vehicle test, both hot and cold, load and no load, both alternators tested good. Same symptom, two different parts , I now feel a little safer to assume that Paul has the right idea regarding the computer incorrectly reading the voltage. While this voltage is being sensed, the ECU will notoutput any data, thus the stall. Immediatley after the stall, the vehicle is little harder starting. I have to put the accelerator to the floor, feather it for 10-15 seconds until it smooths out, then I can continue on my way. Sensor grounds thru the ECU are tested and good.

Please keep us informed! You never know when a similar problem will pop up on another vehicle.

Hey Paul, solution is in the e-mail. Did u get it?

On my GM alternator when it spikes like that it 'always' has a corroded connection on one or more of the main battery cables or grounds.

The bad connection causes the voltage to spike while crossing it, it would seem.

On yours, there is a ground strap from the bell housing to the body that has a tendency to corrode or rot away, if so it can cause a high reading.

The ground cable where it hooks to the engine is a sneaky one, but just those side post terminals can easily be dirty enough to cause it.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: N>

Problem solved! Hi-Lo DMM indicated no transients while encountering igniton shut-down. ECM incorrectly sensing overvoltage. Exchanged ECM with one from the junkyard, problem is now solved. TKS Jim

Excellent! It was your diagnosis that ruled everything else out.