P066C 2015 GMC Sierra Code - Cylinder 2 Glow Plug Control Circuit Low Voltage
Quick Answer
n the diesel engine, air alone is compressed in the cylinder. Common causes include Faulty cylinder #2 glow plug, Cylinder #2 glow plug harness is open or shorted, Cylinder #2 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
- P066C 2015 GMC Sierra indicates Cylinder 2 Glow Plug Control Circuit Low Voltage.
- Common causes
- Common causes include Faulty cylinder #2 glow plug, Cylinder #2 glow plug harness is open or shorted, Cylinder #2 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 P066C 2015 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 P066C 2015 GMC Sierra?
- Faulty cylinder #2 glow plug
- Cylinder #2 glow plug harness is open or shorted
- Cylinder #2 glow plug circuit poor electrical connection
- Faulty Glow Plug Control Module
How to Fix the DTC P066C 2015 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 P066C 2015 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.
Need more information about the P066C 2015 GMC Sierra code?
Need more information on how to fix the P066C 2015 GMC Sierra code? Get Access to Factory Service Manuals
Need Help with the Code?
Get the P066C 2015 GMC Sierra code diagnosed by a professional: Find a repair shop in your area
Frequently Asked Questions about P066C 2015 GMC Sierra Code
1. What does OBDII code P066C mean on a 2015 GMC Sierra?
P066C indicates a low voltage issue in the glow plug control circuit for cylinder 2, which is part of the diesel engine's cold-start system.
2. What are the common symptoms of code P066C in a 2015 GMC Sierra?
Symptoms may include difficulty starting in cold weather, poor engine performance, increased emissions, and an illuminated check engine light.
3. What causes the P066C code to appear on a 2015 GMC Sierra?
Common causes include a faulty glow plug, damaged wiring or connectors in the glow plug circuit, a failed glow plug control module, or a weak battery.
4. How can I diagnose the P066C code in my 2015 GMC Sierra?
Start by inspecting the wiring and connectors for damage or corrosion, testing the glow plug for cylinder 2, and checking the voltage output from the glow plug control module.
5. Can I drive my 2015 GMC Sierra with the P066C code?
While the truck may still run, driving with this code can cause poor cold-start performance and increased emissions. It's best to address the issue promptly.
6. How do I fix the P066C code on a 2015 GMC Sierra?
Repairs may include replacing the faulty glow plug, repairing damaged wiring or connectors, or replacing the glow plug control module if it's defective.
7. How much does it cost to repair the P066C code on a 2015 GMC Sierra?
Repair costs vary but typically range from $100 to $300, depending on whether the glow plug or control module needs replacement.
8. Can a weak battery cause the P066C code on a 2015 GMC Sierra?
Yes, a weak or failing battery can result in insufficient voltage to the glow plug circuit, triggering the P066C code.
9. How can I prevent the P066C code from occurring again?
Regular maintenance, including inspecting the glow plugs, wiring, and battery, can help prevent this code from recurring.
10. Do I need a professional mechanic to fix the P066C code on my 2015 GMC Sierra?
While experienced DIYers may handle basic repairs, consulting a professional mechanic is recommended for accurate diagnostics and repairs.
Discuss the causes and fixes for P066C 2015 GMC Sierra OBDII Code
Code P066C 2015 GMC Sierra comments
No comments found for this page.
Fix Your Car Smarter
Try the New AutoCodes App!
Get complete OBDII diagnostics, repair solutions, and cost estimates, plus AI chat support on demand.
