alternator hookup, no pcm
alternator hookup, no pcm gen 4 motor in an older car. i am using a 160 amp alternator from a 2008 tahoe. do i need to do anything with the two pins on the top to get it to charge? i thought i heard that they were used by the pcm only. i have the rear post hooked up, just trying to cover my bases.
Staging Lane
Joined: Oct 2006
Posts: 70
Likes: 1
I have a similar situation coming up. I am about to start my gen IV in a Jeep and have no Body control Module or Battery Ground Current Sense circuit hooked up. I think the PCM normally gets input from these systems to determine charge level.
How will the PCM know how to charge without these inputs?
How will the PCM know how to charge without these inputs?
Teching In
Joined: Mar 2009
Posts: 33
Likes: 0
From: prescott az
alternator connection one of the pins need a signal, but that signal need a resistor in it [you can use a lamp or a 200 ohm resistor] or as was just stated a alternator shop can change out the module in it to make it into a one wire setup. Ether way I am sure if you take the atlernator in to a auto electric shop they can help you out.
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my buddy from a local parts store tried jumping the pins together then each one to the power terminal. no go. i would like to avoid having the alternator modified. i don't have much time before the car needs to be competition ready. if i need to do something with the two pins, where am i hooking them to and which is Body control Module and Battery Ground Current Sense?
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Verdad Gallardo Staging Lane
Joined: Oct 2006
Posts: 70
Likes: 1
I'm sure it depends on your PCM but the wiring diagrams for an 07' GM truck show a body control module that does a ton of stuff. I guess they started doing this to take badwidth away from the PCM? The PCM is much smaller than 06' and prior. The BCM communicates to the Instrument panel Cluster, Navigation system, Ant-theft, lights, charging system etc. and the PCM looks at all this input along with the Transmision control Module and Fuel system management module then corrects the engine accordingly.
My dilemna is I don't know if the PCM needs BCM input to determine what the charge rate should be? The wiring from alternator to PCM is all intact but without BCM inputs (ie. ground current sensor) will it charge at all?
The ground current sensor is nothing more than a coil they put around the battery ground wire. It sends a signal to the PCM I think? and it determines what the charge should be based on what is being used.
Good luck with your deal.
My dilemna is I don't know if the PCM needs BCM input to determine what the charge rate should be? The wiring from alternator to PCM is all intact but without BCM inputs (ie. ground current sensor) will it charge at all?
The ground current sensor is nothing more than a coil they put around the battery ground wire. It sends a signal to the PCM I think? and it determines what the charge should be based on what is being used.
Good luck with your deal.
the way i have it hooked up now it's wierd. it charges it just enough to not drain the battery. voltmeter on the battery engine off it is 12.6. when i put the voltmeter on the battery with engine running, its 13.10 slowing charging up 13.11....13.12...etc.
Staging Lane
Joined: Oct 2006
Posts: 70
Likes: 1
Well that's not too bad actually. A perfectly good system runs about 13.7 to 14.0 volts so at least you know you are charging.
I don't know what will happen with mine since the ECM normally controls the charge rate but it doesn't have the inputs it expects to make the decision.
I don't know what will happen with mine since the ECM normally controls the charge rate but it doesn't have the inputs it expects to make the decision.
