P0C76: Discharge timing is not a safe-isolation timer

P0C76 is the hybrid battery-system discharge-time diagnostic in this GM controller. The monitored quantity is the rationalized high-voltage inverter-bus reading. The cited condition is a report above 200 volts after 3.5 seconds, with two failures out of two samples in the listed RUN power mode.

Identify what the code actually measures

This is a timing-and-voltage result from the controller, not an instruction for a person to wait 3.5 seconds and access the system. The monitor's absence likewise does not certify electrical isolation or a safe voltage at every component. Only the applicable professional isolation and verification procedure can establish that.

The adjacent discharge-switch circuit diagnostic uses a different test: the voltage change following a commanded discharge event. P0C76's excessive remaining voltage and a circuit-specific discharge failure should therefore not be collapsed into one identical conclusion.

Preserve the event context

A qualified technician needs the original voltage record, discharge-event history, power mode and companion controller faults. The table does not identify a failed resistor, contactor or inverter from P0C76 alone.

This historical calibration does not establish the discharge behavior of every hybrid or electric vehicle. It also supplies no universal component location or replacement decision. Further electrical investigation must match the actual propulsion system and remain within the vehicle-specific high-voltage service procedure.

Source and applicability

15OBDG01 Hybrid Diagnostics, cited controller and monitor only. Historical calibration limits are not universal specifications; per-code vehicle, engine and hardware applicability must be verified.

GM source, physical page 538.