P0AA0: Hybrid/EV Battery Positive Contactor Circuit

The positive main contactor is a high-voltage relay that connects the positive pole of the traction battery to the propulsion bus. P0AA0 is the general fault code for this contactor circuit, used when the controller sees a problem it does not split into stuck closed (P0AA1), stuck open (P0AA2) or the control-circuit codes P0AD9 to P0ADC. No manufacturer documents this exact code publicly; GM, Audi, Jeep and Mitsubishi report the specific siblings instead. NHTSA's Mach-E recall query shows the underlying failure modes: overheated contacts that stay open or weld shut. With the positive side unusable the car may refuse ready mode or drop propulsion; work on it requires high-voltage qualification.

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 enter ready or propulsion-active mode
Hybrid or EV system warning with check engine light
Possible loss of propulsion while driving

Most likely causes

Positive contactor or battery junction box worn or damaged
Fault in the contactor coil feed or its connector
Weak 12 V supply so the contactor does not pull in reliably

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
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 P0AA0 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
A: Hybrid or air and fuel
A0: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0AA0?

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 P0AA0?

The most common causes are: positive contactor or battery junction box worn or damaged; fault in the contactor coil feed or its connector; weak 12 V supply so the contactor does not pull in reliably.

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.