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Thread: Aternator charging rate- cadillac lc3 with e67 pcm

  1. #1
    Potential Tuner
    Join Date
    Feb 2012
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    Aternator charging rate- cadillac lc3 with e67 pcm

    Thought i posted this a couple days ago but think i did something wrong hopefully will post this time. Have only posted once before and that was several years ago.

    I have a cadillac lc3 engine in my hot rod. The oem supercharger has been taken off and replaced with a single turbocharger.

    Everything seemed to be working well. I have been driving the vehicle for a few years and was oblivious to a voltage problem.

    Put the vehicle on a dyno last week and the tuner said that the voltage at the pcm was low. The volt meter on the dash would read between 12.5 and 13 volts and the voltage listed by hp tuners was as low as 11.2 volts. I was lucky that i had brought my battery charger along (odessey 25 amp charger because i run an odessey battery) and put the battery on charge during the dyno session. It brought the voltage at the pcm to above 12.5 v.

    Got home and started checking things out. Noticed that when i started the vehicle the voltage on the gage would go up to 14.8 volts and in almost exactly 120 seconds it would abruptly drop down to 13.0 and even lower when the radiator fans, headlights were turned on. Put in a new alternator and nothing changed. Then started searching the web and it appears that cadillac, in about 2006 +/- went to an alternator that that had a 2 pin plug with a separate pole for the output. The vehicle has the oem e67 pcm and i checked the pin-out schematics which shows the wiring to the 2 pin plug is correct.

    Later found on the web that the e67 controls the alternator and that the e67 makes part of its decision of what to tell the alternator from information it receives from the bcm. My hot rod has no bcm and i don't know how to fix this problem. Hp tuners under the "system" tab it has a table to input alternator information. I don't know how to populate these tables and need help. I talked to the the battery manufacture and they said there battery would have no problem with the battery seeing a constant voltage of 14.5 volts. He said that it was common for many gm vehicles to have 14.5 volts and above while running. This, in turn, should insure that the pcm is always seeing at least 12.5 volts.

    Attached is a copy of the alternator parameters listed in hp tuners.
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