P2E77 code meaning
Hybrid/EV Battery Pack Coolant Temperature Sensor D Circuit High
Powertrain system Generic code P2Exx codes Check engine light
What P2E77 means
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.
P2E77 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P2E77
- Hybrid or check engine warning
- Battery heating may switch on needlessly or behave oddly in winter
Common causes of P2E77
- Most likelySensor D connector unplugged or not latched after cooling system work
- PossibleBroken wire or spread terminal in the sensor D circuit
- Less likelySensor D element open
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Hv battery pack coolant temp sensor dWiring harnessBms
What each part of P2E77 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 77 | The exact fault in that area. |
What to do next
- Note P2E77 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P2E77
What does P2E77 mean?
P2E77 means "Hybrid/EV Battery Pack Coolant Temperature Sensor D Circuit High". P2E77 is set when the signal of battery coolant sensor D rises to or near the reference voltage. It is a generic code, so it means the same on every make.
Is it safe to drive with P2E77?
Drive gently and only to a workshop. With P2E77 the car can go into limp mode (reduced power) to protect itself.
Will P2E77 fail an emissions test?
Yes, it can. P2E77 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P2E77 to fix?
Difficulty: hard. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will P2E77 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.