P066B GMC Code - Cylinder 1 Glow Plug Control Circuit High Voltage
Quick Answer
n the diesel engine, air alone is compressed in the cylinder. Common causes include Faulty cylinder #1 glow plug, Cylinder #1 glow plug harness is open or shorted, Cylinder #1 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
- P066B GMC indicates Cylinder 1 Glow Plug Control Circuit High Voltage.
- Common causes
- Common causes include Faulty cylinder #1 glow plug, Cylinder #1 glow plug harness is open or shorted, Cylinder #1 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 P066B 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 P066B GMC?
- Faulty cylinder #1 glow plug
- Cylinder #1 glow plug harness is open or shorted
- Cylinder #1 glow plug circuit poor electrical connection
- Faulty Glow Plug Control Module
How to Fix the DTC P066B 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 P066B 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.
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Information for Specific GMC Models
- P066B 2014 GMC Sierra — Cylinder 1 Glow Plug Control Circuit High Voltage
- P066B 2015 GMC Sierra — Cylinder 1 Glow Plug Control Circuit High Voltage
- P066B 2016 GMC Sierra — Cylinder 1 Glow Plug Control Circuit High Voltage
- P066B 2017 GMC Sierra — Cylinder 1 Glow Plug Control Circuit High Voltage
- P066B 2018 GMC Sierra — Cylinder 1 Glow Plug Control Circuit High Voltage
Frequently Asked Questions about P066B GMC Code
What does the P066B code mean for a GMC vehicle?
The P066B code indicates a high voltage issue in the glow plug control circuit for cylinder 1, typically related to the diesel engine's starting system.
What are the common symptoms of the P066B code?
Symptoms include difficulty starting the engine in cold weather, a check engine light, rough idling, and decreased engine performance.
What causes the P066B code to trigger?
Common causes include a faulty glow plug, damaged wiring or connectors in the glow plug circuit, a malfunctioning glow plug control module, or a short to voltage.
How do mechanics diagnose the P066B code?
Mechanics use an OBDII scanner to confirm the code, inspect the wiring and connectors, test the glow plug, and check the glow plug control module for proper function.
Can I drive my GMC with the P066B code?
While the vehicle may still be drivable, ignoring the issue can lead to harder starts in cold weather and potential engine damage over time.
How is the P066B code repaired?
Repairs may involve replacing the faulty glow plug, repairing damaged wiring or connectors, or replacing the glow plug control module if defective.
How much does it cost to fix the P066B code on a GMC?
Repair costs vary but typically range from $100 to $300, depending on whether the glow plug or control module needs replacement.
Can a dead battery cause the P066B code?
A weak battery is unlikely to directly cause this code but can exacerbate starting issues. The focus should remain on the glow plug circuit.
Will clearing the P066B code with a scanner fix the issue?
Clearing the code may temporarily turn off the check engine light, but the root cause must be addressed to prevent the code from returning.
How can I prevent the P066B code from reoccurring?
Regularly inspect and maintain the glow plug system, check for damaged wiring or corroded connectors, and address any starting issues promptly.
Discuss the causes and fixes for P066B GMC OBDII Code
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