Powertrain, generic

P0E18 Hybrid/EV Battery Pack Coolant Heater B Control Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P0E18 says the command line of battery coolant heater B reads high when the controller expects it low, for example from contact with a supply wire or an interrupted pulled-up input. No manufacturer documents P0E18 publicly. The risk here is a heater that cannot be switched off. Many coolant heaters therefore carry their own guard; one patent design with a thermistor in the heater housing stops current when the coolant temperature climbs faster than a limit. GM's 2016 Volt groups voltage shorts of its battery heater command into P1EC3 (Type B). CARB requires circuit monitoring of energy-store heating outputs and, where possible, a functional check of heating. A pinched wire against a live feed or a driver that sticks on is typical. Short to ground is P0E17, open circuit P0E16.

Likely causes

Heater B command wire shorted to a voltage source
Controller driver stuck on
Interrupted pulled-up input at heater B

Symptoms

  • Check engine light on
  • Heater B switched off by its overheat protection
  • Battery heating unavailable in cold weather

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 bwiring harnessbms

Related codes

P0E16P0E17P0E19P0E14

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