P068D 2017 GMC Sierra Code - Cylinder 7 Glow Plug Control Circuit High Voltage
Quick Answer
n the diesel engine, air alone is compressed in the cylinder. Common causes include Faulty cylinder #7 glow plug, Cylinder #7 glow plug harness is open or shorted, Cylinder #7 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
- P068D 2017 GMC Sierra indicates Cylinder 7 Glow Plug Control Circuit High Voltage.
- Common causes
- Common causes include Faulty cylinder #7 glow plug, Cylinder #7 glow plug harness is open or shorted, Cylinder #7 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 P068D 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 P068D 2017 GMC Sierra?
- Faulty cylinder #7 glow plug
- Cylinder #7 glow plug harness is open or shorted
- Cylinder #7 glow plug circuit poor electrical connection
- Faulty Glow Plug Control Module
How to Fix the DTC P068D 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 P068D 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 P068D 2017 GMC Sierra Code
1. What does the OBDII code P068D mean on a 2017 GMC Sierra?
P068D indicates a high voltage issue in the Cylinder 7 Glow Plug Control Circuit, which helps the glow plug function properly during cold starts.
2. What are the symptoms of code P068D on a 2017 GMC Sierra?
Common symptoms include difficulty starting the engine in cold weather, rough idling, reduced fuel efficiency, and an illuminated check engine light.
3. What causes the P068D code to appear on a 2017 GMC Sierra?
Possible causes include a faulty glow plug for Cylinder 7, damaged wiring or connectors, a malfunctioning glow plug control module, or corrosion within the circuit.
4. Can I drive my 2017 GMC Sierra with the P068D code?
While the vehicle may be drivable, ignoring the code can lead to poor performance, increased emissions, and potential long-term engine damage, especially in cold weather.
5. How do I fix the P068D code on my 2017 GMC Sierra?
Repairs may include replacing the Cylinder 7 glow plug, repairing damaged wiring or connectors, or replacing the glow plug control module if necessary.
6. How do I diagnose the P068D code on a 2017 GMC Sierra?
Start by inspecting the Cylinder 7 glow plug and its wiring for damage or corrosion, then test the glow plug control module using a multimeter to check for excessive voltage.
7. What tools are needed to repair a P068D code on a 2017 GMC Sierra?
Common tools include a multimeter, OBDII scanner, basic hand tools for removing the glow plug, and potentially dielectric grease for corrosion prevention.
8. How much does it cost to fix the P068D code on a 2017 GMC Sierra?
Repair costs vary but may range from $50 to $200 for a glow plug replacement and up to $300 or more if the glow plug control module needs replacement.
9. Can a bad battery cause the P068D code on a 2017 GMC Sierra?
Yes, a weak or failing battery can cause voltage irregularities that might contribute to glow plug circuit issues, including triggering the P068D code.
10. Does clearing the P068D code fix the problem on a 2017 GMC Sierra?
Clearing the code with an OBDII scanner will temporarily remove the warning, but the underlying issue must be addressed to prevent the code from returning.
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