The P0691 trouble code indicates that the Engine Control Module (ECM) or Powertrain Control Module (PCM) has detected a low voltage condition in the control circuit for Fan 1. Fan 1 is typically associated with the engine cooling system and is controlled by the ECM or PCM to regulate engine temperature. When the voltage in the control circuit drops below the specified threshold, the ECM or PCM triggers the P0691 code.
P0691 Fan 1 Control Circuit Low
Code symptoms P0691.
1. Check Engine Light (CEL) illuminated on the dashboard.
2. Engine may overheat due to insufficient cooling fan operation.
3. Engine performance may be affected, especially during hot weather or heavy loads.
4. Decreased fuel efficiency.
5. Other related trouble codes may be present, depending on the specific issue.
This code is common in brands such as:: Chevrolet, Renault, Ford, Toyota, Nissan, Mercedes Benz, Honda.
Causes of the code P0691.
1. Faulty cooling fan motor or relay.
2. Poor electrical connection in the cooling fan control circuit.
3. Shorted wiring in the cooling fan control circuit.
4. Faulty ECM or PCM.
Code Solutions P0691.
1. Use a diagnostic scanner to retrieve freeze frame data and all associated trouble codes. This information can help pinpoint the root cause of the issue.
2. Inspect the cooling fan motor and relay for any signs of damage or malfunction. Test the components using a multimeter to ensure they are functioning properly. Replace any faulty components as needed.
3. Check the wiring and connectors in the cooling fan control circuit for any signs of damage, corrosion, or loose connections. Repair or replace damaged components as needed.
4. Test the voltage in the cooling fan control circuit using a multimeter. If the voltage is below the specified threshold, diagnose and repair any issues with the ECM or PCM or related components.
5. If the wiring, connectors, and cooling fan motor or relay are in good condition but the code persists, it may indicate a fault in the ECM or PCM. In this case, the ECM or PCM may need to be replaced or reprogrammed by a qualified technician.
6. After any repairs are made, clear the trouble codes and perform a test drive to verify that the issue has been resolved. If the code returns, further diagnosis may be necessary to identify the underlying problem.
7. Follow manufacturer-specific diagnostic procedures outlined in the vehicle’s service manual to accurately diagnose and repair issues related to the cooling fan control circuit. If needed, seek assistance from a qualified technician or dealership.