The P0686 trouble code indicates a low voltage condition in the power relay control circuit of the Engine Control Module (ECM) or Powertrain Control Module (PCM). The ECM or PCM power relay is responsible for providing power to the ECM or PCM, essential for various engine control functions. When the ECM detects low voltage in the power relay control circuit, it triggers the P0686 code.
ECM/PCM Power Relay Control Circuit Low
Code symptoms P0686.
1. Check Engine Light (CEL) illuminated on the dashboard.
2. Engine may not start or may experience difficulty starting.
3. Engine may stall or hesitate during operation.
4. Decreased engine performance and 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 P0686.
1. Faulty ECM or PCM power relay.
2. Poor electrical connection in the power relay control circuit.
3. Shorted or open wiring in the power relay control circuit.
4. Faulty ECM or PCM.
Code Solutions P0686.
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 wiring and connectors in the power relay control circuit for any signs of damage, corrosion, or loose connections. Repair or replace damaged components as needed.
3. Test the ECM or PCM power relay using a multimeter to ensure it is functioning properly. Replace the relay if it is found to be faulty.
4. Check the voltage at the power relay control circuit using a multimeter. If the voltage is low, inspect the battery and charging system for any issues. Repair or replace components as needed to restore proper voltage.
5. If the wiring, connectors, and ECM or PCM power 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 ECM or PCM power relay control circuit. If needed, seek assistance from a qualified technician or dealership.