AutoCodes – Chevrolet – P0678 2018 Chevrolet Silverado

P0678 2018 Chevrolet Silverado Code - Cylinder 8 Glow Plug Circuit Fault

Quick Answer

n the diesel engine, air alone is compressed in the cylinder. 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 2018 Chevrolet Silverado 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 408

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

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Table of contents Created and updated by William Orellana on Mar 24, 2024

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P0678 2018 Chevrolet Silverado Description

n the diesel engine, air alone is compressed in the cylinder. Then, after the air has been compressed, a charge of fuel is sprayed into the cylinder and ignition occurs, due to the heat of compression. Eight glow plugs are used as an aid to starting.
Control of the glow plugs is accomplished by the Glow Plug Control Module. The nominal voltage for the glow plugs is 5.4 volts. When the ignition is turned On, the Glow Plug Control Module applies 7.2 V for 2.2 s, then 5.7 V for 0.8 s, and then 5.4 V until 1200°C (2192°F) is reached. The maximum voltage of the system is 10 V. While the engine is running the voltage will vary between 4.7 - 10 V when in closed loop control to maintain a glow plug temperature that ranges from 1150° - 1180°C (2102° - 2156°F). The temperature and the power consumption are controlled between the Engine Control Module (ECM) and the Glow Plug Control Module within a wide range to suit the engine's pre-heating requirements. Each glow plug is energized individually. This capability yields more optimum heat times for the glow plugs, thus pre - glow times can be kept to a minimum for a short wait to crank times and maximum glow plug durability.

OBDII Code P0678 2018 Chevrolet Silverado - Cylinder 8 Glow Plug Circuit Fault - AutoCodes.com — P0678 2018 Chevrolet Silverado Code - Cylinder 8 Glow Plug Circuit Fault

What does this mean?

What are the Possible Causes of the DTC P0678 2018 Chevrolet Silverado?

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 Control Module (GPCM)

How to Fix the DTC P0678 2018 Chevrolet Silverado?

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 2018 Chevrolet Silverado 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.

Need more information about the P0678 2018 Chevrolet Silverado code?

Need more information on how to fix the P0678 2018 Chevrolet Silverado code? Get Access to Factory Service Manuals

Need Help with the Code?

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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 2018 Chevrolet Silverado Code

1. What are the common symptoms of OBDII code P0678 in a 2018 Chevrolet Silverado?

The common symptoms of code P0678 (Cylinder 8 Glow Plug Circuit Fault) include rough idling, hard starting, decreased fuel efficiency, and the illumination of the check engine light.

2. What are the possible causes of OBDII code P0678 in a 2018 Chevrolet Silverado?

The possible causes of code P0678 can include a faulty glow plug in cylinder 8, damaged wiring or connectors in the glow plug circuit, or a malfunctioning glow plug control module.

3. How can I diagnose the Cylinder 8 Glow Plug Circuit Fault in my 2018 Chevrolet Silverado?

To diagnose code P0678, you can use an OBDII scanner to retrieve the fault code and then visually inspect the glow plug in cylinder 8, check the wiring and connectors for any damage, and test the glow plug control module for proper functionality.

4. Can I continue driving my 2018 Chevrolet Silverado with OBDII code P0678?

It is not recommended to continue driving your vehicle with code P0678 as it can lead to potential engine damage or performance issues. It is best to address the underlying issue as soon as possible.

5. How can I repair OBDII code P0678 in my 2018 Chevrolet Silverado?

To repair code P0678, you may need to replace the glow plug in cylinder 8, repair any damaged wiring or connectors in the circuit, or replace the glow plug control module if necessary.

6. Will resetting the check engine light resolve OBDII code P0678 in my 2018 Chevrolet Silverado?

Simply resetting the check engine light will not resolve the underlying issue causing code P0678. It is important to diagnose and repair the fault to prevent further problems.

7. What impact does OBDII code P0678 have on the performance of a 2018 Chevrolet Silverado?

Code P0678 can affect the performance of your vehicle by causing rough idling, hard starting, decreased fuel efficiency, and potential engine misfires if left unresolved.

8. Can weather conditions affect the occurrence of OBDII code P0678 in a 2018 Chevrolet Silverado?

Extreme cold weather conditions can potentially exacerbate glow plug issues and lead to the triggering of code P0678 in diesel engines like the one in a 2018 Chevrolet Silverado.

9. Is it possible to prevent OBDII code P0678 from occurring in my 2018 Chevrolet Silverado?

Regular maintenance, such as checking and replacing glow plugs as needed, inspecting wiring for damage, and ensuring the glow plug control module is functioning correctly, can help prevent code P0678.

10. How long does it typically take to repair OBDII code P0678 in a 2018 Chevrolet Silverado?

The repair time for code P0678 can vary depending on the exact cause of the issue and the availability of parts. In general, it may take a few hours to a full day to diagnose and repair the fault.