Engine Coolant Heater A Control Circuit High

Common symptoms

What you'll notice

• Check the wiring connections and ensure they are secure and properly connected.
• Inspect the engine coolant temperature sensor for any damage or malfunction and replace if necessary.
• Verify the functionality of the engine coolant heater control module and replace if it is faulty.
• Inspect the engine coolant heater relay and replace if it is defective.
• Finally, if all other solutions have been exhausted, consider replacing the entire engine coolant heater assembly.

Common causes

Most likely first

1. Malfunctioning engine coolant temperature sensor
2. Faulty engine coolant heater control module
3. Short or open circuit in the engine coolant heater control circuit
4. Defective engine coolant heater relay
5. Wiring issue or loose connection in the engine coolant heater circuit

How to diagnose & fix

Work through it in order

1. Engine overheating
2. Intermittent or complete loss of heating in the vehicle cabin
3. Inefficient engine performance, such as reduced power or acceleration
4. Check engine light illuminating on the dashboard
5. Increased fuel consumption