What it means
The HV battery pack coolant heater A reports a control circuit/open 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 A warms the coolant used to bring the high-voltage battery toward its operating temperature in cold conditions. The control module monitors heater A's electrical control path and sets P0E12 when it detects an interruption consistent with an open circuit, so battery preheating may be unavailable.
Common causes
Most likely first.
- Open in heater control wire
- Open heater element
- Pin pushed back out of connector body
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
- Read freeze-frame data and hybrid-system live data to see when the heater A fault occurred and whether a cold battery or failed heating request coincided with it.
- With the vehicle powered down as specified by the manufacturer, inspect heater A's accessible wiring and connectors for damage, loose fit, corrosion, or a terminal pushed back into the connector.
- Check the heater A control circuit for continuity using the manufacturer's wiring diagram and procedure to locate an interruption.
- Test heater A's element and its connector terminals for an open condition according to the manufacturer's specification.
- If the heater and wiring pass, check the control module's command and circuit response using the manufacturer's diagnostic procedure.
Common fixes
- Seat or repair a loose heater A connector or pushed-back terminal.
- Repair an open or damaged heater A control wire.
- Clean or replace damaged heater A connector terminals.
- Replace the heater A element if it tests open.
Can I keep driving?
The vehicle may limit power or charging if battery preheating is unavailable, especially in cold weather. Avoid relying on normal electric range or performance until the fault is repaired, and stop if a red hybrid-system warning or severe power limitation 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.