What it means
The HV battery pack coolant heater B reports a control circuit high condition. Battery preheating may be impaired in cold weather.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Battery coolant heater B warms coolant that helps condition the high-voltage battery in cold weather. The control module monitors heater B's control circuit and sets P0E18 when its voltage is higher than expected, which can indicate a short to battery positive or an open load.
Common causes
Most likely first.
- Wire shorted to B+
- Element open
- Connector pins corroded - high contact resistance
Symptoms
- EV/hybrid system warning light on
- Reduced power output or limp mode
- Charging may fail or be slowed
- Reduced electric range
How to diagnose it
- Review freeze-frame and hybrid-system live data for heater B's requested state, battery temperature, and the conditions when the high-circuit fault appeared.
- With the vehicle powered down as specified by the manufacturer, inspect heater B's wiring and connector for rubbed-through insulation, loose terminals, corrosion, or other damage.
- Use the manufacturer's wiring diagram and procedure to test the heater B control wire for a short to battery positive.
- Test heater B's element and connector for an open load or poor contact according to the manufacturer's specification.
- If wiring and the element pass, check heater B's commanded circuit response and control-module output using the manufacturer's diagnostic procedure.
Common fixes
- Repair heater B wiring shorted to battery positive.
- Restore a loose or damaged heater B connector terminal.
- Clean or replace corroded heater B connector terminals.
- Replace heater B if its element is open.
Can I keep driving?
Battery heating may be impaired in cold weather, and the vehicle may reduce power or charging. Avoid hard acceleration if power is limited and stop if a red hybrid-system warning appears.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.