P0678 2015 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 2015 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.
Code P0678 2015 Chevrolet Silverado Description
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.
What are the Possible Causes of the DTC P0678 2015 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 2015 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 2015 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.
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Frequently Asked Questions about P0678 2015 Chevrolet Silverado Code
What does the OBDII code P0678 mean in a 2015 Chevrolet Silverado?
P0678 indicates a fault in the glow plug circuit for cylinder 8, meaning the vehicle's computer has detected an issue with the performance or electrical connection of the glow plug.
What are the common symptoms of code P0678 in a 2015 Chevrolet Silverado?
Symptoms may include difficulty starting the engine in cold weather, reduced fuel efficiency, a rough idle, or the check engine light being illuminated.
What causes the P0678 code to appear in a 2015 Chevrolet Silverado?
Common causes include a failed glow plug, damaged wiring or connectors in the glow plug circuit, a faulty glow plug control module, or corrosion in the electrical connections.
Can I drive my 2015 Chevrolet Silverado with the P0678 code?
While the vehicle may still run, driving with this code can lead to poor engine performance, especially in cold weather, and could cause further damage if left unresolved.
How do I diagnose a P0678 code on a 2015 Chevrolet Silverado?
Start by inspecting the wiring and connectors for cylinder 8's glow plug. Use a multimeter to test the glow plug's resistance and check the output from the glow plug control module to ensure proper function.
What tools are needed to fix the P0678 code?
You'll typically need a multimeter, a diagnostic scan tool, and basic hand tools. Depending on the issue, you may also need replacement parts like a new glow plug or wiring.
How do I replace the glow plug for cylinder 8 in a 2015 Chevrolet Silverado?
First, disconnect the battery. Locate cylinder 8’s glow plug, remove the electrical connector, and use a deep socket to unscrew the glow plug. Install the new glow plug, tighten it to the manufacturer's specifications, and reconnect the electrical connector.
What is the cost to repair a P0678 code on a 2015 Chevrolet Silverado?
The repair cost can vary, but replacing a glow plug typically costs $50–$150 for parts and labor, while fixing wiring or replacing a glow plug control module may cost more.
What happens if I ignore the P0678 code in my 2015 Chevrolet Silverado?
Ignoring this code can lead to starting difficulties, especially in cold weather, reduced fuel economy, and potential damage to other engine components over time.
Can extreme weather cause a P0678 code?
Yes, extreme cold can exacerbate issues with glow plugs or their circuits, as they are essential for starting the engine in lower temperatures.
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