P0D64: Battery cooling-fan enable circuit is open while off

P0D64 refers to the hybrid/EV battery pack cooling fan enable circuit/open. The 2018 GM row identifies fan 1 and checks the output-enable circuit while the cooling-fan enable command is false.

An off command does not mean the circuit is unmonitored

The documented open-circuit feedback band is 1.14–2.81 V. System voltage must be above 10.2 V, and 16 failed samples among 20, taken every 250 milliseconds, meet the five-second evaluation. The reporting classification is Type B, two trips.

That command state is important. A fan that is not rotating while it is commanded off is not the evidence for P0D64. The controller is evaluating the electrical condition of the enable path, not requiring off-state airflow.

Separate electrical continuity from fan performance

Retain the enable command and feedback voltage from the event. A circuit-open assessment and a failure to achieve requested speed are different diagnostic findings; replacing the motor solely because the code contains “fan” would skip that distinction.

After a repair, verify the enable output under the correct off-state conditions and perform the applicable fan checks. A successful brief fan command does not automatically demonstrate that the off-state open-circuit monitor passes. Use the exact vehicle wiring and diagnostic procedure; these voltage values are not a universal pin test. Battery-system access near protected high-voltage components must remain within qualified service.

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 951.