Positive contactor worn, faulty or failing to close; Low 12 V auxiliary battery voltage preventing the contactor coil from being energised properly; Wiring or connector fault in the contactor control or feedback circuit, such as corrosion, a loose pin or damage; Blown or faulty high-voltage fuse or open circuit in the high-voltage path, causing a voltage feedback fault; Fault in the battery management or control unit, or outdated software where a known issue exists for that model; Faulty voltage sensing circuit giving a false reading.

P0AA2

Hybrid/EV Battery Positive Contactor Circuit Stuck Open.

Generic
Powertrain
Generic code
High severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
A: AreaHybrid propulsion
A2: FaultThe specific fault in that area

What it means

P0AA2 is a generic powertrain code meaning the hybrid or EV battery control system has detected that the positive high-voltage contactor is stuck open, or is not closing when commanded. The control unit commands the contactor to close and then checks voltage or feedback on the circuit. If the expected voltage or contactor status does not appear, it sets the code and may disable high-voltage drive.

Symptoms

Hybrid or EV system warning light on the dashboard
Car will not go into READY mode or will not start
Loss of electric drive or reduced power, possibly running on the petrol engine only (hybrids)
Limp-home or reduced performance mode
Clicking sound, or no click, from the battery pack area when switching on
Charging not starting on plug-in models

Possible causes

Positive contactor worn, faulty or failing to closelikely
Low 12 V auxiliary battery voltage preventing the contactor coil from being energised properlylikely
Wiring or connector fault in the contactor control or feedback circuit, such as corrosion, a loose pin or damagepossible
Blown or faulty high-voltage fuse or open circuit in the high-voltage path, causing a voltage feedback faultpossible
Fault in the battery management or control unit, or outdated software where a known issue exists for that modelpossible
Faulty voltage sensing circuit giving a false readingrare

How to diagnose

Read all stored and pending codes and the freeze frame data, noting any other high-voltage, contactor or 12 V supply codes
Test the 12 V auxiliary battery state of health and charging system, and fix any low-voltage issue first
Visually inspect the battery pack area, harness and connectors for damage, water ingress, corrosion or loose connections, following the manufacturer's high-voltage safety procedure
Listen for contactor operation at power-up and use live data to compare commanded and actual contactor status, if the model supports it
Check the contactor control circuit supply, ground and signal for continuity and voltage drop, using the wiring diagram for the model
Following the manufacturer's high-voltage isolation procedure, check the high-voltage fuse or service disconnect and the pack voltage readings
Check for applicable technical bulletins and software updates for the vehicle; procedures vary by model

How to fix

Charge or replace the weak 12 V auxiliary battery and clear the code once the system is healthy
Repair or replace damaged wiring, terminals or connectors in the contactor circuit
Replace the faulty positive contactor or the contactor assembly, as specified for the model
Replace a blown high-voltage fuse only after finding and fixing the cause
Replace or update the battery control unit software or unit if a fault or outdated calibration is confirmed

Can I keep driving?

High severity

Do not rely on driving the car. It may fail to start or lose drive, and work on the high-voltage system should only be done by a suitably trained technician. If it does still run, limit use and have it checked promptly.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.