P2D56Hybrid/EV Battery Pack Coolant Temperature Sensor C 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
- P2D56 points to a coolant temperature signal from sensor C that jumps around faster than liquid in the battery loop can really change temperature, while mostly staying inside the electrical limits. No manufacturer documents P2D56 publicly. GM runs such a test for sensor A as P0C46 in table 19OBDG01: every 100 ms the step to the previous inlet reading is taken, ten absolute steps are summed, and a sum above 64 °C counts as a failure; 4 s within 5 s set a Type B code, and the test pauses while the hard faults P0C44 or P0C45 are active. For sensor B, Volvo's TJ 36929 notes that P0CD900 after charging in air above 20 °C can be a false detection cured by software 3.2.4. CARB requires circuit continuity checks. Loose pins and moving harnesses are the usual suspects.
- What you may notice
- Warning light that comes and goes
- Sensor C value jumps in live data, especially when wiggling the harness
- Usually no noticeable driveability change
- Likely causes
- LikelyLoose or corroded terminal in the sensor C connector
- PossibleHarness rubbing or moving with the battery, causing brief interruptions
- RareDetection logic reacting to normal conditions (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: €80 – €700
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.