CUSTOMER CONCERN Vehicle will not crank after hybrid-system repair and DTC P0633 is stored. CAUSE The theft-deterrent system lost the required immobilizer identification during the repair. CORRECTION Perform the immobilizer relearn procedure.

CUSTOMER CONCERN Customer states the engine oil-pressure gauge intermittently drops to 0 psi without abnormal engine noise. DTC P0521 is stored. CAUSE Mechanical oil-pressure testing remained normal while the scan-tool and dash readings dropped, confirming a failed engine oil-pressure sensor. CORRECTION Remove and replace engine oil-pressure sensor and inspect or replace the sender screen beneath it. Clear DTC P0521 and verify stable oil-pressure readings.

CUSTOMER CONCERN Customer states the engine will not crank after a front-end collision. No relevant DTC is initially stored. CAUSE Serial Data Gateway Module data showed Crash Detected, confirming the high-voltage impact-detection system had disabled propulsion. CORRECTION Inspect and repair high-voltage impact sensor circuit as required, perform HPCM 300-volt impact-status reset and secured high-voltage DTC reset, then verify normal cranking.

CUSTOMER CONCERN Customer states the engine intermittently stalls during an automatic restart and usually will not restart. The Service Hybrid System message is displayed. CAUSE Testing under GM bulletin PIT4808 confirmed an internal failure in the hybrid battery pack. CORRECTION Remove and replace hybrid battery pack. Perform sequential EBCM, HCP, ECM, TCM and BECM programming with current calibrations and verify automatic start operation.

CUSTOMER CONCERN Customer states the vehicle will not crank. DTCs P0AC4, U1888, U1875 and U1878 are stored. CAUSE DLC resistance, fuse-feed and expansion-bus testing isolated an open or high-resistance circuit in the drive-motor generator power-inverter module wiring. CORRECTION Repair drive-motor generator power-inverter module wiring and connector terminals. Clear network and hybrid DTCs and verify module communication and normal cranking.