P0E18Hybrid/EV Battery Pack Coolant Heater B Control 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
- 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.
- What you may notice
- Check engine light on
- Heater B switched off by its overheat protection
- Battery heating unavailable in cold weather
- Likely causes
- LikelyHeater B command wire shorted to a voltage source
- PossibleController driver stuck on
- RareInterrupted pulled-up input at heater B
- 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: €80 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.