Powertrain, generic

P0E12 Hybrid/EV Battery Pack Coolant Heater A Control Circuit/Open

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P0E12 concerns the command circuit of battery coolant heater A, the electric element that warms the coolant sent to the hybrid or EV battery when the pack is too cold for charging or full power. The controller flags it when this circuit is open or otherwise electrically faulty. No manufacturer documents P0E12 publicly. GM's 2016 Volt shows the same check under its own code P1EC3: above 10.2 V system voltage, 20 failed readings within 40 samples taken every 100 ms set a Type B code. CARB requires every electronic output used to heat the energy store to be checked for circuit faults. Typical finds are a cracked conductor, an unseated connector or a dead output stage. In frost the car may then limit charging or rely on the engine. Shorts to ground or voltage are P0E13 and P0E14.

Likely causes

Broken or chafed wire in the heater A command circuit
Loose, corroded or unlocked connector at the heater or controller
Open circuit inside the heater A assembly
Failed output driver in the controlling module

Symptoms

  • Check engine light on
  • Slow or reduced charging in cold weather
  • Engine runs more often than usual on cold days
  • Reduced electric power until the pack warms up

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–1,500
Time1–4 h

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

Parts involved

hv battery pack coolant heater awiring harnessbms

Related codes

P0E13P0E14P0E15P0E16P0C47

References: gsi.ext.gm.com, law.cornell.edu.