P2E77Hybrid/EV Battery Pack Coolant Temperature Sensor D Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P2E77 is set when the signal of battery coolant sensor D rises to or near the reference voltage. In a pull-up NTC circuit that is the signature of an open: a disconnected plug, a broken wire, a spread pin or a sensor element that has gone open, and the controller then sees a coolant temperature colder than physically plausible. No manufacturer documents P2E77 publicly. GM's sensor B analogue P0CD8 fails below -40 °C, an ADC count above 3823, persisting for 1.75 s of a 2.5 s window; the 2011 Volt runs it only while the 5 V reference of the battery controller is fault-free. CARB requires such out-of-range checks. In cold weather battery heating may misjudge the loop; the low counterpart is P2E76.
- What you may notice
- Hybrid or check engine warning
- Battery heating may switch on needlessly or behave oddly in winter
- Likely causes
- LikelySensor D connector unplugged or not latched after cooling system work
- PossibleBroken wire or spread terminal in the sensor D circuit
- RareSensor D element open
- 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: €60 – €700
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.