Ok, My 2000 Caravan 2.4l, 486,000 miles lit up the battery light yesterday still drove over 200 miles without running battery dead, I have a bluetooth reader that works with my tablet. Monitoring voltage it sits at about 11.1 but every 5-10 mins jumps up to 13.5-14.2 The auto parts store put the tester on the battery and said the battery is good the alternator is bad. I have seen many threads that suggest that it can be eitbher the alternator or the PCM due to the voltage regulation done in the PCM. Is there a way to determine which is bad the alternator or the PCM.

I also started getting a misfire which if I understand correctly could be the PCM or just the low voltage.

Thanks for any input.

Bob

 

IF it is the alternator, you need to find out soon. Running the car with a bad alternator, there is the risk of damaging the PCM field coil driver....then you'll need both.

Only way to tell is do the tests for the field coil DTC...while it's happening.

 

It is sitting while I figure it out, Can i test this with multi meter or scanner and software?

 

Thanks for the reply by the way.

 

When I scan for fault codes I get some random wheel sensor errors.

 

On the rear of the alternator is a 2 pin plug, dark green wire and dark green with orange tracer. Running you should have 12 volts to the dark green with orange tracer. That is the feed for the brushes. The dark green wire is the wire the PCM grounds to get the alternator to charge. If you were to back probe that wire and ground it, the system should full field. If the system is running at 11 volts and you ground that wire and have 11 volts still and have battery voltage to the other side of the alternator, the alternator is bad.

 

I will test tomorrow, So if the voltage increases when I ground the dk green wire the problem is with the regulator in the PCM. if it doesn't change then it's the alternator, Correct?

 

If you ground and nothing, bad alternator. If you ground and it changes, then you have to ohm both wires to the PCM and make sure you don't have an open, then most likely a PCM issue.

 

Thanks alot, Test showed it was the alternator. I replaced it today and all is well again 486,000 miles and still going....

 

Nice, I always total them before I can cross the 350K mark. Not my fault mind you....2 rearendings and one T-bone.