P0A02: Motor Electronics Coolant Temperature Sensor A Circuit Low
What to do
The car may become sluggish and refuse to use electric drive. If that happens after only a short, gentle journey, the reading is more likely to be at fault than the cooling — but it still needs diagnosing rather than ignoring, because the same symptom is what a real overheat produces.
What this code means
The power electronics coolant temperature circuit reads below its valid voltage range, normally a short to ground. These are thermistors whose resistance falls as temperature rises, so a short to ground is electrically identical to coolant that is impossibly hot.
The module responds to that reading exactly as it would to a genuine emergency: it restricts the power the drive motor and inverter are allowed to handle, and may decline to use electric drive at all. The car becomes noticeably slow and the hybrid warning appears, on a cooling system that is working perfectly.
Likely causes
Start here
- Wiring shorted to ground · moderate
- Faulty inverter coolant temperature sensor · moderate
Less common
- Corroded or loose connector · easy
- Damaged wiring harness · moderate
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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