P2E78Hybrid/EV Battery Pack Coolant Temperature Sensor D Circuit Intermittent/Erratic
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- P2E78 stands for a coolant temperature from sensor D that jumps around, mostly without leaving the electrical limits. A liquid loop changes temperature slowly, so fast swings point to a loose contact rather than to the coolant. No manufacturer documents P2E78 publicly. GM's 2019 hybrid table shows a matching test for inlet sensor A (P0C46): it adds up the absolute changes between ten successive readings and counts a sum above 64 °C as a fail; 4 s out of 5 s set a two-trip Type B code, and it is skipped while the hard faults P0C44/P0C45 are present. Volvo found that P0CD900 for sensor B on 2021–22 PHEVs after charging in warm weather might be a spurious entry; software release 3.2.4 resolves it (TJ 36929). CARB requires circuit continuity monitoring.
- What you may notice
- Warning light that comes and goes
- Coolant temperature in live data jumping
- Likely causes
- LikelyLoose or fretting terminal in the sensor D connector
- PossibleHarness rubbing through near moving or vibrating parts
- RareFalse detection by controller software (update)
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €0 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.