P0AA2Hybrid/EV Battery Positive Contactor Circuit Stuck Open
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P0AA2 means the positive main contactor does not close, or does not conduct, when the controller commands it closed, so the high-voltage bus cannot be energised from the pack. Audi documents it for the 2020-2022 Q5 e quattro and 2021-2022 A7 e quattro plug-in hybrids: the car does not start and the battery management module stores P0AA2 (often with P0AA5). Audi traces rare cases to oxidised contact surfaces in the battery junction box after long standing or high humidity, and first prescribes repeated ignition cycles and an EV road test before replacing the junction box. GM lists the code among high-voltage faults for which Ultium EV pack data must be collected. Unlike P0AA1, the contacts are open, not welded.
- What you may notice
- Vehicle does not start or reach ready mode
- Service high voltage battery or hybrid warning message
- Possible sudden loss of propulsion if the contactor opens while driving
- Likely causes
- LikelyOxidised contact surfaces after long standing or high humidity (Audi)
- PossibleFailed battery junction box or burnt contactor
- PossibleContactor coil not energised due to wiring or 12 V supply fault
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €100 – €3,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.