Powertrain, generic · Hybrid propulsion

P0AA2 Hybrid/EV Battery Positive Contactor Circuit Stuck Open

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Oxidised contact surfaces after long standing or high humidity (Audi)
Failed battery junction box or burnt contactor
Contactor coil not energised due to wiring or 12 V supply fault

Symptoms

  • 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

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–3,000
Time0.5–6 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

hv battery positive contactorbmswiring harness

Related codes

P0AA1P0AA5P0AA0P0AD9

References: static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov.