P0C89: Sensor I performance compares module-group temperatures

P0C89 is the battery-temperature sensor I performance diagnostic in the cited GM table. The monitor compares I with the average temperature reported by the other module groups. Its finding is relative plausibility, not simply whether the battery has exceeded a universal temperature ceiling.

A low or high report can fail

The absolute difference must be greater than 20°C. Because the comparison is absolute, a reading below the reference can qualify just as a reading above it can. Preserve the actual direction and magnitude of the disagreement for the workshop.

GM requires 50 failed samples among 67, with 100-millisecond evaluation intervals. The monitor therefore records repeated deviation. A single outlying scan value does not demonstrate the full condition and should not replace the controller's event history.

Use a valid reference

The temperature-rationality fault bundle must be false. Retain relevant companion faults when considering whether the comparison was enabled. An absent new P0C89 during an inhibited period cannot confirm a healthy I measurement.

The code alone does not establish whether the difference is a real thermal variation or a sensor/reporting issue. A qualified high-voltage technician must use the correct battery service information to distinguish those possibilities and map I to physical hardware. The table contains no universal connector location, sensor resistance specification or mandatory battery replacement. Verification should explain the comparison under valid operating prerequisites.

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 586.