This is my first post in years, possibly ever
I am having problems with the voltage output of my alternator. The engine is a 2008 Cadillac LC3 using an e67 pcm and the alternator is from the same year Cadillac. Basically the alternator has 3 wires for hook up. A 2 pin plug and the 3rd for the 12v + output. The alternator is grounded through the case to the engine. Have good grounds to engine and body. Have been running the car for years with no problems. "Ignorance is bliss" It appears that this is a newer style alternator which GM started using about 2007 that relies on the e67 pcm as a voltage regulator. Check the wiring from the E67 to the 2 pin plug and it appears correct.
Put the car on the dyno last week and the tuner showed me that the pcm voltage was low. I hooked up a 25 amp Odessey battery charger to the vehicle, because it has an Odessey battery, during the dyno session and everything proceeded well.
Got home and started to investigate the problem. When you first start the vehicle the alternator puts out 14.5 volts. After about 2 minutes the voltage drops to 13.0 The voltage that I read will go as low as 11.2 when read through my OBDII port while it always stays above 12.4 on my dash gauge when I turn on the headlights and radiator fans etc. I put in a new alternator and nothing changed. Searched the web and it appears the E67 gets help from the BCM to control the voltage output of the alternator. This engine is in a stand alone application and there is no BCM. Under the System tab on HP Tuners there is a section for Alternator parameters. I have attached a screen shot of this. I would like to set my alternator output to like 14.8 volts which seems to keep my OBDII voltage above 12.5 does anyone know how I should populate this data? I don't want to fry the pcm so am reluctant to make guesses. Hopefully someone has had the same problem and knows a solution.