P0AA2: Hybrid/EV Battery Positive Contactor Circuit Stuck Open

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.

High severity. Can I keep driving?If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

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

Most 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

What to check, in order

Start with the simplest. You can tick off each step.

Read the codes with a hybrid-compatible scanner and write down the freeze frame data
Check the continuity of the wire between the component and the control module.
Make sure the battery cooling air intake is clean
Check the 12 V auxiliary battery, which can also trigger warnings
Leave any high-voltage measurements to a specialized repair shop

Good to know

It can trigger limp mode.
It affects emissions.

What each character of P0AA2 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
A: Hybrid or air and fuel
A2: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0AA2?

If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

What causes code P0AA2?

The most common causes are: 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.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.