P0678 – BMW DTC

BMW DTC P0678 – Cylinder 8 Glow Plug Circuit/Open

DTC P0678 meaning on BMW

DTC P0678 indicates a fault in the glow plug circuit for cylinder 8 in a BMW vehicle. The Engine Control Module (ECM) monitors the glow plug circuit to ensure proper functioning during cold starts. When this diagnostic trouble code is triggered, it means that there is an open circuit or a fault in the wiring related to the glow plug in cylinder 8.

BMW DTC P0678 symptoms

Symptoms of DTC P0678 in a BMW may include:

• Hard starting, especially in cold weather
• Rough idling or misfiring
• Reduced engine performance
• Check Engine Light (CEL) illuminated on the dashboard

BMW DTC P0678 causes

The common causes of DTC P0678 in a BMW include:

• Defective glow plug in cylinder 8
• Wiring harness issues, such as open circuits or shorts
• Faulty glow plug relay
• ECM software issues

BMW DTC P0678 seriousness

While DTC P0678 may not cause immediate drivability issues, it is important to address this fault promptly to ensure proper engine performance, especially during cold starts. Ignoring this fault can lead to further complications and potential damage to the engine over time.

How to diagnose DTC P0678 on BMW

To diagnose DTC P0678 on a BMW, you can follow these steps:

1. Use a diagnostic scanner to retrieve the fault code and verify it is P0678.
2. Inspect the glow plug in cylinder 8 for any physical damage or signs of wear.
3. Check the wiring harness connected to the glow plug for continuity and any visible damage.
4. Test the glow plug relay for proper operation.
5. Perform a resistance test on the glow plug to determine if it is functioning correctly.

How to fix DTC P0678 on BMW

To fix DTC P0678 on a BMW, you can take the following steps:

1. Replace the glow plug in cylinder 8 if it is found to be faulty.
2. Repair any damaged wiring in the glow plug circuit.
3. Replace the glow plug relay if it is malfunctioning.
4. Clear the fault code using a diagnostic scanner after the repairs are completed.

How to erase DTC P0678 on BMW

To erase DTC P0678 on a BMW, follow these steps:

1. Connect a diagnostic scanner to the vehicle’s OBD-II port.
2. Access the ECM module and navigate to the fault code menu.
3. Select the option to clear the fault code associated with P0678.
4. Confirm the deletion of the fault code and ensure that the Check Engine Light is no longer illuminated.

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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