P0AA2: Hybrid/EV Battery Positive Contactor Circuit Stuck Open
What to do
Twelve-volt battery first — a hybrid that will not wake has a tired small battery far more often than a failed contactor, and testing it costs nothing. Then the P0A27 service-plug check if recent work applies. The contactor itself is the last and most expensive answer.
What this code means
The positive contactor did not close when commanded — the pack cannot connect, and the car cannot wake.
The presentation is total and clean: no READY, everything twelve-volt working normally, nothing dramatic stored beforehand. The suspect list runs cheapest-first with unusual clarity: the twelve-volt battery (a contactor coil needs healthy voltage to pull in — the commonest cause and the cheapest fix on this page), the service plug if anyone has been near the pack (P0A27's story), the coil's wiring and fuse, and finally the contactor itself with worn or burnt contacts that no longer carry current when closed.
Likely causes
Start here
- Failing 12 volt battery · easy
Less common
- High voltage service plug not fully seated · easy
- Open circuit in control wiring · moderate
- Faulty battery contactor · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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