Code Definition

P0AA2 (227) — Hybrid battery positive contactor circuit stuck open

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

About P0AA2

P0AA2 is a generic (obd-ii standard) powertrain diagnostic trouble code recorded for Toyota vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P0AA2 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 P0AA2 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

Subcode 227 is set when the hybrid vehicle control ECU or battery ECU detects that the positive high-voltage contactor has failed to close after being commanded on. This determination is made based on a lack of voltage buildup or current flow in the high-voltage system downstream of the contactor, indicating that the circuit remains open when it should be closed.

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