AutoCodes – Audi – P0678 Audi

P0678 Audi Code - Cylinder 8 Glow Plug Circuit Fault

Quick Answer

The glow plug system is used to assist in providing the heat required to begin combustion during cold engine temperatures. Common causes include Faulty cylinder #8 glow plug, Cylinder #8 glow plug harness is open or shorted, Cylinder #8 glow plug circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P0678 Audi indicates Cylinder 8 Glow Plug Circuit Fault.
Common causes: Common causes include Faulty cylinder #8 glow plug, Cylinder #8 glow plug harness is open or shorted, Cylinder #8 glow plug circuit poor electrical connection.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 464

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jul 18, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P0678 Audi Description

The glow plug system is used to assist in providing the heat required to begin combustion during cold engine temperatures. The glow plugs are heated before and during cranking, as well as initial engine operation. The Engine Control Module (ECM) controls the glow plug ON times by monitoring coolant temperature and glow plug voltage. The California Glow Plug system has eight individual glow plug supply circuits between the controller and the glow plugs. If the feedback voltage from the controller to the ECM is not within range, the ECM sets the OBDII code.

OBDII Code P0678 Audi - Cylinder 8 Glow Plug Circuit Fault - AutoCodes.com — P0678 Audi Code - Cylinder 8 Glow Plug Circuit Fault

What does this mean?

What are the Possible Causes of the DTC P0678 Audi?

Faulty cylinder #8 glow plug
Cylinder #8 glow plug harness is open or shorted
Cylinder #8 glow plug circuit poor electrical connection
Faulty glow plug module

How to Fix the DTC P0678 Audi?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0678 Audi code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0678 Audi Code

1. What does the OBDII code P0678 mean on an Audi?

P0678 indicates a fault in the glow plug circuit for cylinder 8, suggesting an issue with the glow plug or its related wiring and components.

2. What are the symptoms of a P0678 code in an Audi?

Common symptoms include difficulty starting the engine in cold conditions, rough idle, reduced engine performance, and an illuminated check engine light.

3. What causes the P0678 code to appear?

The code is typically caused by a faulty glow plug, damaged wiring, corroded connections, a defective glow plug control module, or issues with the cylinder 8 glow plug circuit.

4. How do I diagnose the P0678 code on my Audi?

Start by inspecting the glow plug, wiring, and connections for cylinder 8. Use a multimeter to check for continuity in the circuit and test the glow plug's resistance. If necessary, scan the control module for additional fault codes.

5. Can I drive my Audi with a P0678 code?

While the vehicle may still run, driving with this code can lead to poor performance, harder cold starts, and potential long-term engine damage if left unresolved.

6. How do I fix the P0678 code on an Audi?

Repairs may include replacing the faulty glow plug, repairing or replacing damaged wiring, cleaning corroded connections, or replacing the glow plug control module if itâ€™s defective.

7. How much does it cost to repair a P0678 code in an Audi?

The cost varies depending on the issue. Replacing a single glow plug typically costs $50â€“$150, while repairing wiring or replacing the control module may cost more depending on labor rates and parts pricing.

8. Can a bad glow plug cause engine damage?

A single bad glow plug wonâ€™t typically cause immediate engine damage, but it can lead to harder starts, increased emissions, and stress on other engine components over time.

9. How long do Audi glow plugs typically last?

Glow plugs usually last between 60,000 and 100,000 miles, but their lifespan can vary depending on driving conditions and maintenance.

10. Do I need to replace all the glow plugs if one fails?

While not always necessary, replacing all glow plugs at the same time is often recommended to ensure consistent performance and avoid future failures.