P0E18 code meaning
Hybrid/EV Battery Pack Coolant Heater B Control Circuit High
Powertrain system Generic code P0Exx codes Check engine light
What P0E18 means
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.
P0E18 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0E18
- Check engine light on
- Heater B switched off by its overheat protection
- Battery heating unavailable in cold weather
Common causes of P0E18
- Most likelyHeater B command wire shorted to a voltage source
- PossibleController driver stuck on
- Less likelyInterrupted pulled-up input at heater B
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 heater bWiring harnessBms
What each part of P0E18 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 18 | The exact fault in that area. |
What to do next
- Note P0E18 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 P0E18
What does P0E18 mean?
P0E18 means "Hybrid/EV Battery Pack Coolant Heater B Control Circuit High". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P0E18?
Drive gently and only to a workshop. With P0E18 the car can go into limp mode (reduced power) to protect itself.
Will P0E18 fail an emissions test?
Yes, it can. P0E18 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 P0E18 to fix?
Difficulty: hard. A typical repair takes 1 to 4 hours of work. This is a job for a workshop.
Will P0E18 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.