Circuit/System Testing

WARNING: Always perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed.
The High Voltage Disabling procedure will perform the following tasks:

Identify how to disable high voltage.
Identify how to test for the presence of high voltage.
Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed.

Failure to follow the procedures exactly as written may result in serious injury or death.

With the ignition OFF, disconnect the module harness connectors listed below, if equipped, one at a time. After each disconnect, retest the BCM for current DTCs. DTC U2099 should remain current.
- Drive motor generator battery control module (BECM) (RPO HP2) - X 1
- Electronic brake control module (EBCM) - X 1
- Electronic suspension control (ESC) module - X 1
- Fuel pump flow control module (FPCM) - X 1
- Power steering control module (PSCM) (RPO HP2) - X 1
- If the DTC becomes history, replace the module disconnected before the DTC became history.

IMPORTANT: If the vehicle is not equipped with RPO HP2 proceed to step 6.

Perform the High Voltage Disabling procedure.
Ignition OFF, disconnect harness connector X1 of the BECM.
Reconnect the 12-volt battery.
Test the BCM for current DTCs. DTC U2099 should remain current.
- If the DTC becomes history, replace the BECM.
Ignition OFF, disconnect the harness connector X 3 at the BCM.
With the above harness connectors still disconnected, test for infinite resistance between the high speed GMLAN serial data wake up circuit terminal 19 and ground.
- If less than the specified value, test the wake up circuit for a short to ground.
If all circuits test normal and DTC is current, replace the BCM.