P0AE4

What it means

P0AE4 is a generic powertrain code meaning the hybrid or EV control unit has detected a problem in the control circuit of the high voltage battery precharge contactor A, with the circuit reading as open. The precharge contactor, usually working with a resistor, lets the high voltage system charge up gradually before the main contactors close. The control unit commanded the contactor and saw no proper response from its circuit, so it set the code and will normally stop the high voltage system from engaging.

Symptoms

• Hybrid or EV system warning light on the dashboard
• Car will not go into READY mode or will not start
• Loss of drive or reduced power
• Malfunction indicator lamp lit
• Intermittent no-start that sometimes clears after switching off and on again

Possible causes

• Wiring or connector fault in the precharge contactor control circuit (open circuit, corrosion, loose or pushed-back pin)likely
• Faulty precharge contactor or relay with an open coillikely
• Low or faulty 12 V auxiliary battery or poor battery terminal connections causing unstable supply to the contactor circuitpossible
• Blown fuse or fault in the supply or ground to the contactor circuitpossible
• Fault inside the battery management or hybrid control unit driver circuitrare
• Water ingress or physical damage to the high voltage battery pack connectors or junction arearare

How to diagnose

1. Read all stored and pending codes and note freeze frame data, checking for related high voltage, contactor or 12 V supply faults.
2. Check the 12 V auxiliary battery condition, terminal tightness and charging voltage, as low voltage can cause false contactor faults.
3. Inspect the relevant fuses and the visible wiring and connectors for damage, corrosion, water or chafing, following the manufacturer's high voltage safety procedure.
4. Check the manufacturer's information for the model to find the contactor location and circuit layout, as this varies between makes and models.
5. With the high voltage system safely isolated by a trained technician, measure the contactor coil resistance and compare it with the specification.
6. Check the control circuit for continuity, short to ground or short to supply between the control unit and the contactor, plus the supply and ground.
7. Use a scan tool's live data or actuator tests, if supported, to see whether the control unit commands the contactor and the circuit responds.
8. Check for any technical bulletins or software updates relevant to the vehicle before replacing the control unit.

How to fix

• Repair or replace damaged wiring, terminals or connectors in the contactor control circuit.
• Replace the faulty precharge contactor or relay as specified by the manufacturer, using a trained high voltage technician.
• Replace or charge the 12 V battery and clean and tighten its connections if it is weak or poorly connected.
• Replace any blown fuse after finding and correcting the cause of the failure.
• Repair or replace the battery management or hybrid control unit only after the wiring and contactor are proved good, and update the calibration if an outdated one is a known cause.

Can I keep driving?

Nearby codes

• P0AE3GenericHybrid/EV Battery Precharge Contactor Circuit Stuck Open
• P0AE5GenericHybrid/EV Battery Precharge Contactor A Control Circuit Range/Performance