Is there a C5 dis-assembly around anywhere? The C5 PCM is very picky about the alternator interface and I was hoping to see what the alternator tests are and possibly figure out why it throws a charging fault even when the connected alternator functions perfectly fine.
What DTC is being set ?
It seems that P1637 or P1638 are the DTC codes for the charging circuit. There is also a error message that appears in the driver information system. I have found that the DTC's can be set to no error reported and the charging system error can still appear in the DIC.
People typically have issues with these cars popping up the error message on startup with a replacement alternator even though the alternator functions perfectly fine and after resetting the initial warning message it doesn't come back until the car is started again.
I was hoping to get some insight into why the PCM is so damn picky.
Last edited by lionelhutz; 07-16-2014 at 06:35 PM.
Not sure what year / OS you are working with. Not all platforms were wired the same with respect to the alternator. Some used only the alternator "L" terminal - often wired to a simple "idiot light". Others used both the alternator "L" and "F" terminals (Corvettes used both I believe).
If this is in an actual Corvette, make certain the alternator is wired as a Corvette would have been, and confirm the alternator you are trying to use has all of these terminals.
If this is not in a Corvette, you can turn off the P1638 DTC (Field Duty Cycle), and wire a bulb into the "L" terminal circuit.
I don't own a Corvette, but this seems to be a very common problem - based a quick Google search.
Here is one of many discussions that seemed relevant ....
http://www.google.com/url?sa=t&rct=j...71126742,d.aWw
Yes, all C5's used both L and F terminals. Ideas for troubleshooting a car aren't what I'm looking for. I'm looking for the specific testing the PCM does when it decides to make the charging system fault appear on the DIC to gain some insight into why certain replacement alternators cause an issue on startup.
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