Powertrain, generic (extended)

P2E77 Hybrid/EV Battery Pack Coolant Temperature Sensor D Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Sensor D connector unplugged or not latched after cooling system work
Broken wire or spread terminal in the sensor D circuit
Sensor D element open

Symptoms

  • Hybrid or check engine warning
  • Battery heating may switch on needlessly or behave oddly in winter

Repair estimate

DifficultyHardWorkshop job
Parts and labour€60–700
Time0.5–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

hv battery pack coolant temp sensor dwiring harnessbms

Related codes

P2E74P2E76P2D55P0CD8P0C45

References: law.cornell.edu, gsi.ext.gm.com, gsi.ext.gm.com, en.wikipedia.org.