P066C GMC 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 GMC 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 GMC 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 GMC?
- 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 GMC?
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 GMC 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 GMC code?
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Need Help with the Code?
Get the P066C GMC code diagnosed by a professional: Find a repair shop in your area
Information for Specific GMC Models
- P066C 2014 GMC Sierra — Cylinder 2 Glow Plug Control Circuit Low Voltage
- P066C 2015 GMC Sierra — Cylinder 2 Glow Plug Control Circuit Low Voltage
- P066C 2016 GMC Sierra — Cylinder 2 Glow Plug Control Circuit Low Voltage
- P066C 2017 GMC Sierra — Cylinder 2 Glow Plug Control Circuit Low Voltage
- P066C 2018 GMC Sierra — Cylinder 2 Glow Plug Control Circuit Low Voltage
Frequently Asked Questions about P066C GMC Code
1. What does the OBDII code P066C mean for a GMC vehicle?
The P066C code indicates a low voltage issue in the glow plug control circuit for cylinder 2 in a GMC vehicle.
2. What are the common symptoms of the P066C code?
Symptoms may include difficulty starting the engine in cold weather, a check engine light, rough idling, or reduced engine performance.
3. What causes the P066C code to appear?
The code can be caused by a faulty glow plug, damaged wiring or connectors, a malfunctioning glow plug control module, or a weak vehicle battery.
4. Can driving with the P066C code damage my GMC vehicle?
Driving with this code may cause poor engine performance in cold weather and could eventually lead to further damage if left unresolved.
5. How do I diagnose the P066C code in my GMC vehicle?
Diagnosis involves checking the glow plug, inspecting the wiring and connectors for damage, and testing the glow plug control module with a multimeter.
6. How can I fix the P066C code?
Repairs may include replacing the faulty glow plug, repairing damaged wiring or connectors, or replacing the glow plug control module if necessary.
7. How much does it cost to fix the P066C code in a GMC?
The repair cost depends on the issue but typically ranges from $100 to $300 for parts and labor, depending on whether the glow plug or control module needs replacement.
8. Can a weak battery trigger the P066C code?
Yes, a weak or failing battery can cause low voltage issues in the glow plug control circuit, potentially triggering this code.
9. Will clearing the code with a scanner fix the issue?
Clearing the code may temporarily turn off the check engine light, but the underlying issue must be resolved to prevent the code from returning.
10. Can I replace the glow plug for cylinder 2 myself?
If you have basic mechanical knowledge and the proper tools, you can replace the glow plug yourself, but professional diagnosis is recommended to ensure accurate repairs.
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