P0686 – BMW DTC

BMW DTC P0686 – ECM/PCM Power Relay Control Circuit Low

DTC P0686 meaning on BMW

DTC P0686 on a BMW indicates a problem with the ECM/PCM power relay control circuit. This fault code is triggered when the powertrain control module (PCM) detects that the voltage signal from the relay control circuit is lower than the specified threshold.

BMW DTC P0686 symptoms

Symptoms of DTC P0686 on a BMW may include:

• Engine stalling or not starting
• Loss of power
• Check Engine Light (CEL) illuminated on the dashboard
• Difficulty in accelerating

BMW DTC P0686 causes

The common causes of DTC P0686 on a BMW are:

• Defective ECM/PCM power relay
• Faulty wiring or poor connections in the power relay control circuit
• Low battery voltage
• Corrosion or damage to relay terminals

BMW DTC P0686 seriousness

DTC P0686 should be addressed promptly as it can lead to drivability issues and potential engine damage if left unresolved. Ignoring this fault code may result in the vehicle becoming inoperable.

How to diagnose DTC P0686 on BMW

To diagnose DTC P0686 on a BMW, follow these steps:

1. Use a diagnostic scanner to retrieve the fault code and freeze frame data
2. Inspect the ECM/PCM power relay and its connections for any visible damage or corrosion
3. Check the battery voltage to ensure it is within the specified range
4. Perform a continuity test on the power relay control circuit to identify any open or short circuits

How to fix DTC P0686 on BMW

To fix DTC P0686 on a BMW, consider the following steps:

1. Replace the ECM/PCM power relay if it is found to be faulty
2. Repair any damaged wiring or connectors in the power relay control circuit
3. Clean any corrosion from the relay terminals and ensure a secure connection
4. Reset the fault code and test drive the vehicle to confirm the issue has been resolved

How to erase DTC P0686 on BMW

To erase DTC P0686 on a BMW, you can:

1. Use a diagnostic scanner to clear the fault code from the PCM memory
2. Disconnect the vehicle’s battery for a few minutes to reset the PCM
3. After clearing the code, perform a final scan to ensure the fault code has been successfully erased

Recommended tools & DTC Scanners for BMW

Best Diagnostic App for modern BMWs: BimmerLink

Recommended Bluetooth adapter for Bimmerlink: OBDLink CX

Cable adapter for Bimmerlink: Enet Cable USB Type C

For older BMWs we recommend: Autel AutoLink AL319 (2024 version)

Easy-to-use Multimeter for reliable diagnostics: AstroAI Auto-ranging Multimeter

Some of the links on this page may be affiliate links, which means we may earn a small commission if you make a purchase. This helps us keep our DTC database up to date and provide valuable content for free. We only recommend products that we have tested and believe to be the best in their class.