Failed high voltage discharge circuit

The circuit that bleeds the high-voltage capacitors down to a safe voltage after shutdown has failed, so the system stays energised longer than it should.

This is the one electrical fault in the corpus whose main consequence is to the next person who touches the car rather than to the car itself. When an electrified vehicle is switched off, the contactors open and the energy still stored in the inverter's capacitors is deliberately drained through a discharge path, so that within a short specified time nothing is at a dangerous potential. Every safe working practice around these vehicles assumes that happens.

When it does not, the vehicle looks exactly as it always does. There is no noise, no warning light that means this specific thing, and no way to tell by looking. The car is off, the dashboard is dark, and the inverter is still at several hundred volts. The familiar "switch it off and wait a few minutes" rule — which is what most people rely on, including many general workshops — is precisely the rule this fault makes untrue.

The causes are few. A bleed resistor that has gone open, which is the commonest; a control fault in the discharge circuit; or a contactor that has not opened at all, in which case the capacitors are not merely undrained but still connected to the pack.

The practical rule: a vehicle reporting a discharge-timing fault is treated as live regardless of its ignition state, and that has to be communicated to whoever works on it. The fault is repairable and not expensive; the hazard is entirely in not knowing about it.