Circuit/System Verification

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.

Verify that there are no DTCs in the APM that disable the 42-volt circuit, no engine-stall DTCs in the ECM, and no U-codes in any module.
- If there are any of the specified DTCs, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
Engine running, accessories OFF, measure and record the battery voltage at the battery terminals. The voltage should be between 12.6-15.0 volts.
- If not within the specified range, refer to Charging System Test .
Engine running, observe the scan tool PSCM Intermediate Voltage parameter. The voltage should be 37.5-50 volts.
- If not within the specified range, refer to Voltage Out Of Range At All Times .
Engine running, rotate the steering wheel left and right while stationary. Observe the scan tool PSCM Intermediate Voltage parameter. The voltage should remain greater than 37.5 volts.
- If the voltage is less than the specified range only when turning the steering wheel, refer to Low Voltage When Turning .
Operate the vehicle on a bumpy road. Observe the scan tool APM 42V Circuit Maximum parameter. The scan tool 42V Circuit Maximum parameter should be less than 50 volts.
- If the voltage is greater than the specified range, replace the PSCM.