Battery light stays on

ALVINIRT

MEMBER
2005 MAZDA 121
110,000 MILES

At first, car was running pefectly fine. I pressed the alarm button to find my car in the parking lot. After driving it for almost an hour, the battery light started to flicker. I brought it to my mechanic. He check the battery, it was ok, then changed the alternator including the alternator belt and he test drove it. Now the battery light stays steadily on, and he said that the transmission starts to " clunk out" He then runned it through a computer to check the real problem, now he is saying that the problem is caused by a computer called PCM. He told me that he tested the PCM in my car and found out there is no electricity going to the alternator. I am looking at an additional $ 1000.00 to fix it. I really needed your expert opinion because I think that the PCM is not the cause of all this. Thank you.

1 Reply

HMAC300

MECHANIC
48,601 POSTS

I looked up a tribute as I couldn't find a 121 model. There are 3 fusible links between teh alternator and battery junction box. Those are 2 gray wires and one dark blue. If any of those are burnt up you will have the problem. However if the pcm doesn't send a signal to the alternator it won't charge eitehr. But that doesn't mean the pcm is bad, it can/could be a bad connection at either end and that must be checked out before replaceing a pcm.