P0686 Engine Control Module Power Relay Control Circuit Low

OBD2 Code: P0686

Description: Engine control module power relay control circuit low.

Definition: This code indicates that the engine control module (ECM) has detected a problem with the power relay control circuit, specifically that the voltage is lower than expected. This can lead to issues with starting or running the vehicle as it affects the ECM’s ability to receive adequate power.

p0686 – Engine Control Module Power Relay Control Circuit Low

Typical Severity: Moderate

Common Causes

P0686 – Engine Control Module Power Relay Control Circuit Low

Common causes:

• Faulty engine control module power relay
• Short circuit in the engine control module power relay wiring
• Loose or poor connection at the engine control module power relay
• Corrosion in the engine control module power relay circuit
• Defective engine control module (rare)

 

Common Misdiagnosis

OBD2 Code: P0686

Description: Engine Control Module Power Relay Control Circuit Low

Common Misdiagnosis: Replacing the engine control module (ECM) without checking the power relay or wiring issues.

 

Common Diagnostic Steps

OBD2 Code: P0686

Description: Engine Control Module (ECM) Power Relay Control Circuit Low

Common Diagnostic Steps:

• Check the ECM power relay for proper operation and replace if faulty.
• Inspect the wiring and connectors between the ECM and the power relay for damage or corrosion.
• Test the battery voltage to ensure it is within specifications.
• Verify that all related fuses are intact and functioning properly.
• Use a multimeter to check for continuity in the control circuit from the ECM to the relay.
• If applicable, use a scan tool to monitor live data and confirm if there are any other related codes present.
• If no faults are found, consider testing or replacing the ECM as a last resort after ruling out all other possibilities.