If you are getting that code, the computer (PCM) is seeing 18+ volts from the alt or the battery is above 16 volts. You could have a faulty alt, a wiring issue between the alt and PCM, or a bad battery.
Run this test and let me know what you find.
KOER at idle, check voltage at the white/blue wire at the alt connection. It should be between 3v and 8v at idle.
Check voltage at the light green/white wire at alt connection. It should be 0.7v to 2v.
If the voltage at the connector are okay, you need to check the white/blue wire back to the PCM (pin 30) and the light green /white wire back to the PCM (pin53). You are checking for an open circuit or a short to power.
If all checks out correct there, check voltages at PCM pin 104. The same wires should produce the same voltage from the alt.
Let me know what you find.
Joe
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Monday, July 14th, 2014 AT 8:39 PM