Engine Coolant Heater B Control Circuit Performance

Common symptoms

What you'll notice

• Check the engine coolant level and ensure it is at the appropriate level.
• Inspect for any leaks in the engine coolant system and repair as necessary.
• Test and replace the engine coolant temperature sensor if it is malfunctioning.
• Inspect the wiring and connections related to the engine coolant heater circuit and repair any issues found.
• If all else fails, consider replacing the engine coolant heater itself.

Common causes

Most likely first

1. Faulty engine coolant heater control module
2. Malfunctioning engine coolant temperature sensor
3. Wiring or connection issues related to the engine coolant heater control circuit
4. Defective engine coolant heater relay
5. Low coolant level leading to poor performance of the engine coolant heater

How to diagnose & fix

Work through it in order

1. Engine overheating
2. Poor fuel efficiency
3. Engine misfires or stumbles
4. Reduced engine power
5. Check engine light illuminates