P0691 Fault Code

Fan 1 Control Circuit Low

• What does that mean?
• Symptoms
• Causes
• Solutions

The P0691 fault code indicates a problem with the fan 1 control circuit being low. This typically means that the engine control module (ECM) has detected that the voltage signal sent to the fan control relay or the fan itself is lower than expected. A properly functioning fan is essential for regulating engine temperature and preventing overheating.

• The fan plays a crucial role in cooling the engine and the radiator.
• Monitoring the electrical system for faults is essential for vehicle reliability.

What are the symptoms of the P0691 code?

When the P0691 code triggers, you may observe the following symptoms:

• The engine may overheat due to inadequate cooling from the fan.
• The cooling fan may not engage, leading to higher engine temperatures.
• Various warning lights may illuminate on the dashboard, such as the check engine light or temperature warning light.
• You might notice unusual engine performance or increases in fuel consumption.

What causes the P0691 code?

Several factors can lead to a P0691 fault code, including:

• Damaged wiring or connectors in the fan control circuit.
• A faulty fan control relay that fails to provide sufficient voltage to the fan.
• A defective engine coolant temperature sensor that might send erroneous signals to the ECM.
• An actual issue with the fan motor itself, causing it to draw too little current.

How to fix P0691?

To resolve the P0691 fault code, follow these steps:

1. Inspect the fan control circuit for any obvious signs of damage such as frayed wires or corroded connectors.
2. Test the voltage at the fan connector while the engine is running to ensure it meets the specifications outlined in the vehicle service manual.
3. Replace any damaged relays, wiring, or connectors discovered during the inspection.
4. If the wiring appears intact, test the fan motor itself to ensure it is functioning properly, and replace it if necessary.
5. Clear the fault codes and monitor if the P0691 code reappears after repairs are made.