Code Definition

P0AA5 — Hybrid battery negative contactor circuit stuck open

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P0AA5

P0AA5 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P0AA5 is stored, the module has detected an open (broken or disconnected) electrical path in the monitored circuit.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P0AA5 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

This DTC is set when the hybrid/EV control module commands the hybrid battery negative contactor to close, but no voltage is detected on the high-voltage bus, indicating the circuit remains open. The module uses feedback from voltage sensors to verify the contactor's operation. If the system does not respond with the expected voltage rise, it interprets the contactor as stuck open.

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