P0A0B: High Voltage System Interlock Circuit A Performance
Do not keep driving
Have the vehicle recovered rather than driven, and do not investigate it yourself. The car is refusing to connect its high-voltage battery because the safety circuit that protects anyone working on it is no longer giving a reading that can be trusted — that is the system being careful, not a fault to be worked around. If the problem seems to come and go with the weather, say so: that points at moisture or corrosion in a connector rather than at a failed part, and it is a far cheaper repair.
What this code means
The interlock loop is electrically continuous but its measured behaviour is outside what the module expects — the circuit is there, and the module does not trust what it is reading from it.
This is the awkward member of the family, because nothing is obviously disconnected. The plain circuit code at P0A0A is set by a loop that is open, which normally means something is genuinely unlatched and can be found by looking. Here the loop closes, but the resistance through it has drifted — corrosion spreading across a pin face, a partially backed-out terminal, moisture in a connector — so the signal returns at a level the module cannot distinguish from a partial break with confidence.
The module's response is to assume the worst, and that is the correct design. An interlock it cannot read reliably is an interlock that cannot be relied on to detect a genuinely open cover, so the contactors stay open and the pack stays isolated. A safety circuit that gave itself the benefit of the doubt would be worse than none.
Because the fault is a degraded contact rather than a broken one, it often follows weather, and a car that failed on a wet morning and passed by the afternoon is describing exactly this. Everything under P0A0A about not investigating this yourself applies here without qualification.
Likely causes
Start here
- Corroded interlock connector pin · specialist
- Water ingress into a high voltage connector · specialist
- High voltage cover or connector not latched · specialist
Less common
- Damaged interlock wiring · specialist
- High voltage service plug not fully seated · 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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