Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Circuit/System Description
The high voltage crash impact detection (HVCID) sensor utilizes a unidirectional 2-wire circuit. The HVCID modulates current on the interface to send ID, State of Health, and collision status to the serial data gateway module (SDGM). The SDGM serves as a power source and a ground for the HVCID. When the ignition is turned ON and input power from the SDGM is first detected, the HVCID responds by performing internal diagnostics and sending an ID to the SDGM. The HVCID continually communicates status messages to the SDGM, which determines if a fault is present in the HVCID circuit.
The SDGM transmits a GMLAN message to the Hybrid Powertrain Control Module (HPCM) whenever a HVCID sensor fault is detected. The HPCM will then disable the vehicle by opening the high voltage contactor relays until this fault condition is cleared and the HPCM is properly reset.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.