Cause
Welded battery contactor
One of the high-voltage contactors connecting the traction battery to the rest of the car has fused shut and can no longer open.
A contactor is a very large relay, and it is the only thing that disconnects the pack. Turn the car off, crash it, or trip any safety interlock, and these are what open — de-energising everything downstream. The whole high-voltage safety architecture rests on them being able to.
They weld for a physical reason worth understanding, because it explains why precharge exists. An inverter contains substantial capacitors, and closing a contactor onto empty capacitors draws an enormous inrush current for a few milliseconds — enough to melt and fuse the contact faces. So the car first charges those capacitors gently through a resistor, and only then closes the main contactor onto a circuit already at voltage. A failed precharge resistor therefore does not merely log a code: it destroys the contactor it was protecting, and the two faults arrive together.
Why this matters more than most electrical faults is what it takes away. A welded contactor means the pack cannot be isolated — the vehicle is live downstream whether or not it is switched on, and it will still be live after a collision. A car reporting this should not be worked on by anyone without high-voltage training, and should not be assumed safe because it is switched off. The car itself will normally refuse to operate, which is correct.
The usual detection is a self-test at shutdown: the module opens the contactors and checks that the voltage downstream actually falls. One that does not is welded.
Typically specialist work. Needs equipment or training most home workshops do not have.
Some of these codes mean you should stop driving
5 of the 20 codes this can cause indicate a fault where continuing to drive risks damage or is unsafe. Which one you have matters more than the cause does — read the code's own page before deciding.
Codes this can cause (20)
Codes where this is a likely explanation first, rather than merely a possible one.
- P0AA1 Hybrid/EV Battery Positive Contactor Circuit Stuck Closed Likely for this code High
- P0AA4 Hybrid/EV Battery Negative Contactor Circuit Stuck Closed Likely for this code High
- P0AE2 Hybrid/EV Battery Precharge Contactor Circuit Stuck Closed Likely for this code High
- P0C76 Hybrid/EV Battery System Discharge Time Too Long Likely for this code High
- P0C77 Hybrid/EV Battery System Precharge Time Too Short Likely for this code High
- P0D08 Battery Charging System Positive Contactor A Stuck Closed Likely for this code High
- P0D0F Battery Charging System Negative Contactor A Stuck Closed Likely for this code High
- P0D25 Battery Charger System Precharge Time Too Short Likely for this code High
- P0E6A Battery Charging System Precharge Contactor Circuit Likely for this code High
- P0E6B Battery Charging System Precharge Contactor Circuit Stuck Closed Likely for this code High
- P0E6C Battery Charging System Precharge Contactor Circuit Stuck Open Likely for this code High
- P0DA8 Hybrid/EV Battery Voltage/Drive Motor A Inverter Voltage Correlation Stop driving High
- P0DA9 Hybrid/EV Battery Voltage/Drive Motor B Inverter Voltage Correlation Stop driving High
- P0E2E Battery Charger A Fuse Stop driving Critical
- P0E2F High Voltage Fuse B Stop driving Critical
- P0E30 High Voltage Fuse C Stop driving Critical
- P0C0B Drive Motor A Inverter Power Supply Circuit/Open High
- P0C0C Drive Motor A Inverter Power Supply Circuit Low Moderate
- P0C0E Drive Motor B Inverter Power Supply Circuit/Open High
- P0C0F Drive Motor B Inverter Power Supply Circuit Low Moderate
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.
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