Alright im a little unclear with which unit does what. Im pretty sure the PCM does the voltage regulation for the alternator, correct? I had some problems with voltage regulation so i did a voltage regulator bypass to fix the problem. However I would like to replace whichever unit is bad.
Ive also had problems with hard starting issues that were all fixed by unplugging the batteries and letting it sit for a minute or two. This leads me to believe that is a problem with whichever electronic box controls ignition. Also, I have had problems with code readers not being able to read anything from the OBDII port. My question is, which unit (pcm or ecm) controlls ignition and which one does a code scanner read if plugged into the OBDII port. And just for clarification, the PCM is on the passenger side firewall and the ECM is on the side of the engine correct?

Thanks for any info.

 

no one knows?

 

PCM should do the voltage regulator and the ODB2 communication.

 

i don't know what do OBDII readings..but PCM is the one behind the air filter box, on the firewall and ECM is mounted on the drivers side of the engine
PCM is the POWERTRAIN CONTROL MODULE

rob

 

Badme is correct.
PCM controls tranny, intake heaters, A/C clutch, votage regulation, OBD11, speedo signal, and I'm sure more. The ECM and VP44 work in unision for fuel delivery and retains history amoung other things about fuel usage and loading factors. It generlly can only be read by Dealer and Cummins. So fault codes are generally passed on to PCM.