P0AE3: Precharge bus voltage did not rise as expected

P0AE3 names a hybrid/EV battery precharge contactor circuit stuck open condition. The 2018 GM HPC2/VICM common table diagnoses it from insufficient propulsion negative-bus voltage during precharge. It does not directly observe the contactor's internal mechanical movement.

The sequence supplies the meaning

The listed failure threshold is bus voltage below 5 V. The precharge contactor state must have been closed for 0.090 seconds, the propulsion negative contactor must be open, the bus-voltage measurement must not be faulted, and battery heating mode must be off.

Eight failed samples out of ten at 12.5-millisecond intervals satisfy the row's evaluation. The test executes once per controller wake-up during precharge and is classified Type A, one trip.

A low voltage outside this sequence is different evidence

Retain the precharge state, elapsed time, bus-voltage validity and actual voltage together. A low bus reading when precharge has not been requested does not reproduce this test. Likewise, a sensor fault can make a voltage-based conclusion unreliable, which is why measurement validity is an enable condition.

The vehicle-specific procedure must distinguish a nonresponsive contactor path from other causes of the missing voltage response. Do not bypass precharge or bridge contactors to test that hypothesis. High-voltage diagnosis requires qualified personnel. Verification should include the prescribed precharge sequence and an eligible monitor result, not just an erased stored code.

Source and applicability

This explanation follows the documented GM monitor, not a verified application to every vehicle with this code. Confirm the vehicle, reporting module and calibration in current service information. GM diagnostic table, physical page 944.