Circuit/System Testing

WARNING: This page is about a different car, the 2008 GMC Yukon and 2008 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.

Turn the ignition key to the OFF position.
Disconnect the 42 volt X2 harness connector at the APM.
Turn the ignition key to ON. Do not go to START.
Use the scan tool APM Intermediate Voltage Control under the APM special functions list to turn on the 42 volt circuit.
- If the APM Intermediate Voltage is not between 40 and 44 volts, replace the APM.
- If the APM Intermediate Voltage is between 40 and 44 volts, the problem is not in the APM. This DTC can set for the following external reasons:

High voltage contactor relays opening any time the APM is doing 42 volt conversion.
The high voltage system is greater than 390 volts or less than 216 volts during 42 volt conversion. Extreme cold weather conditions may occasionally cause the high voltage system to be greater than 390 volts.
The 12 volt circuit is less than 6.7 volts during 42 volt conversion.
A short circuit condition on the 42 volt circuit which causes the APM to produce greater than 60 amps.