ECM Voltage Regulator is the problem?

[silvernblack]

Working on a friends 1997 3500. It comes with PCM controlled voltage regulator (PCM VR). It did have a bad battery so replaced that. She gambled and bought a brandy new 136 amp alternator but the alternator still does not charge. I told her we didn't know it was the alternator but she went ahead and bought the new alternator. So I installed it.

My question: How do I determine whether the PCM Voltage Regulator (PCM VR) is working appropriately? I am really suspecting the PCM VR but do NOT see any codes.....and I have one of them MUCAR 892BT code scanner with bidirectional controls and all kinds of garbage.

The PCM does NOT have any codes set as far as I can see. If there is something specific I should be looking for I am willing to learn and look again.

I am really suspecting the PCV VR but don't how to prove it. Any guidance would be appreciated.

 

[Slinge]

you need a scan tool (maybe alfa obd ).
That will energize the alternator field.
Then use your test light to confirm that pcm is performing that function.

 

[silvernblack]

I tried the option of energizing the field with my scantool. It was there. But it gave me the response that it did not work. (forger the exact words but it could not do when commanded to do so).

 

[Slinge]

The truck needs to be off
I think
Key on not running