P0C80: Sensor G temperature data is erratic

P0C80 identifies a hybrid/EV battery temperature sensor G intermittent/erratic circuit fault. The 2018 GM diagnostic records excessive signal movement within a short window. It does not directly declare a cooling-system failure.

How the evidence accumulates

GM integrates the absolute changes over ten samples and compares the result with a threshold above 10. Four bad evaluations out of five, taken at 100-millisecond intervals, satisfy the stated failure requirement. The source does not specify that integrated number as a standalone battery-temperature limit.

System voltage must be above 10.2 V, and the listed battery-interface communication fault group must be absent. The code has Type B, two-trip reporting in this table. An intermittent connection is one possible cause discussed in the monitor description.

What a normal reading cannot show

Sensor G can return to a plausible reading after an unstable episode. A single later value therefore cannot demonstrate that its wiring and measurement path are consistently sound. A time history is more relevant to this particular diagnostic than a lone temperature measurement.

Before physical inspection, confirm the vehicle's channel G mapping and the original communication state. A verified correction should produce stable, credible data through an enabled monitor run. Do not assume sensor G corresponds to a universal cell or connector number. Work inside the traction-battery sensing system requires qualified high-voltage personnel and the applicable procedure.

Source and applicability

This explanation follows the documented GM monitor, not a verified application to every vehicle with this code. Confirm the vehicle, reporting module and calibration in current service information. GM diagnostic table, physical page 908.