P0688 – BMW DTC

BMW DTC P0688 – ECM/PCM Power Relay Sense Circuit/Open

DTC P0688 meaning on BMW

The Diagnostic Trouble Code (DTC) P0688 for BMW refers to the ECM/PCM Power Relay Sense Circuit/Open. This code indicates that there is an open circuit or a fault in the power relay sense circuit of the Engine Control Module (ECM) or Powertrain Control Module (PCM).

BMW DTC P0688 symptoms

Symptoms of the BMW DTC P0688 may include:

• Engine stalling or not starting
• Loss of power
• Check Engine Light (CEL) illuminated on the dashboard
• Reduced fuel efficiency

BMW DTC P0688 causes

Common causes of the BMW DTC P0688 include:

• Defective ECM/PCM power relay
• Wiring issues in the power relay sense circuit
• Corrosion or poor connections in the circuit
• Faulty ECM/PCM

BMW DTC P0688 seriousness

The BMW DTC P0688 is a serious issue that should be addressed promptly. Ignoring this code can lead to potential engine performance issues, stalling, or even the vehicle not starting at all.

How to diagnose DTC P0688 on BMW

To diagnose the DTC P0688 on a BMW, you can follow these steps:

1. Use a diagnostic scanner to retrieve the fault codes.
2. Inspect the power relay and its connections for any visible damage or corrosion.
3. Check the wiring in the power relay sense circuit for continuity and proper connections.
4. Test the ECM/PCM for proper functionality.

How to fix DTC P0688 on BMW

To fix the DTC P0688 on a BMW, you can try the following:

1. Replace the defective ECM/PCM power relay.
2. Repair any damaged or corroded wiring in the power relay sense circuit.
3. Clean and secure any loose connections in the circuit.
4. If the ECM/PCM is faulty, it may need to be replaced or reprogrammed.

How to erase DTC P0688 on BMW

To erase the DTC P0688 on a BMW, you can:

1. Use a diagnostic scanner to clear the fault codes.
2. After fixing the underlying issue, drive the vehicle to allow the ECM/PCM to relearn and verify the repair.

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

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