P0674 2017 GMC Sierra Code - Cylinder 4 Glow Plug Circuit Fault
Quick Answer
n the diesel engine, air alone is compressed in the cylinder. Common causes include Faulty cylinder #4 glow plug, Cylinder #4 glow plug harness is open or shorted, Cylinder #4 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
- P0674 2017 GMC Sierra indicates Cylinder 4 Glow Plug Circuit Fault.
- Common causes
- Common causes include Faulty cylinder #4 glow plug, Cylinder #4 glow plug harness is open or shorted, Cylinder #4 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 P0674 2017 GMC Sierra 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 P0674 2017 GMC Sierra?
- Faulty cylinder #4 glow plug
- Cylinder #4 glow plug harness is open or shorted
- Cylinder #4 glow plug circuit poor electrical connection
- Faulty Glow Plug Control Module (GPCM)
How to Fix the DTC P0674 2017 GMC Sierra?
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 P0674 2017 GMC Sierra 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 P0674 2017 GMC Sierra Code
1. What does the OBDII code P0674 mean on a 2017 GMC Sierra?
P0674 indicates a fault in the glow plug circuit for cylinder 4, which may affect the engine's ability to start in cold conditions.
2. What are the common symptoms of code P0674 in a 2017 GMC Sierra?
Symptoms include hard starting in cold weather, rough idling, decreased engine performance, and the illumination of the check engine light.
3. What causes the P0674 code on a 2017 GMC Sierra?
Common causes include a faulty glow plug, damaged glow plug wiring, a bad glow plug control module, or poor electrical connections in the circuit.
4. How do I diagnose the P0674 code on my 2017 GMC Sierra?
Diagnosis typically involves scanning for codes, visually inspecting the glow plug and its wiring, testing the resistance of the cylinder 4 glow plug, and checking the functionality of the glow plug control module.
5. Can I drive my 2017 GMC Sierra with a P0674 code?
While the vehicle may still be drivable, prolonged operation with this code can lead to starting issues in cold weather and possible engine damage over time.
6. How do I fix the P0674 code on a 2017 GMC Sierra?
Repairs may include replacing the faulty glow plug, repairing damaged wiring, cleaning or reconnecting electrical connections, or replacing the glow plug control module if needed.
7. How much does it cost to fix the P0674 code on a 2017 GMC Sierra?
The cost can vary. Replacing a glow plug typically costs $50–$150, while more extensive repairs, like fixing wiring or replacing the control module, can cost $200–$500 or more.
8. Can a bad glow plug cause engine damage in my 2017 GMC Sierra?
A single bad glow plug usually won’t cause immediate damage, but consistent starting issues and misfires can put strain on other engine components over time.
9. How can I prevent the P0674 code from recurring?
Regular maintenance, including inspecting glow plugs and their circuits, can help prevent this issue. Addressing any starting issues promptly can also reduce the risk.
10. Is a professional mechanic required to fix the P0674 code?
While experienced DIYers can replace a glow plug or inspect wiring, complex issues like control module failure may require a professional mechanic's expertise.
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