Engine Coolant Heater A Control Circuit Performance

Common symptoms

What you'll notice

• Check the engine coolant levels and ensure it is at the appropriate level.
• Inspect the engine coolant heater control circuit wiring for any damaged or disconnected wires and repair if necessary.
• Test the engine coolant heater control module to verify if it is functioning properly and replace if required.
• Inspect the engine coolant temperature sensor and ensure it is working accurately. Replace if necessary.
• Check the engine coolant heater relay and replace if it is faulty.

Common causes

Most likely first

1. Faulty engine coolant temperature sensor
2. Malfunctioning engine coolant heater control module
3. Wiring issue or connection problem in the engine coolant heater control circuit
4. Failed engine coolant heater
5. Faulty engine control module (ECM)

How to diagnose & fix

Work through it in order

1. Engine overheating
2. Coolant leaks
3. Fluctuating temperature gauge
4. Lack of heat inside the car
5. Illuminated check engine light