AutoCodes – GMC – P068C 2015 GMC Sierra

P068C 2015 GMC Sierra Code - Cylinder 7 Glow Plug Control Circuit Low 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: P068C 2015 GMC Sierra indicates Cylinder 7 Glow Plug Control Circuit Low 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.

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Code Popularity 166

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Mar 24, 2024

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P068C 2015 GMC Sierra Description

n the diesel engine, air alone is compressed in the cylinder. Then, after the air has been compressed, a charge of fuel is sprayed into the cylinder and ignition occurs, due to the heat of compression. Eight glow plugs are used as an aid to starting.
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.

OBDII Code P068C 2015 GMC Sierra - Cylinder 7 Glow Plug Control Circuit Low Voltage - AutoCodes.com — P068C 2015 GMC Sierra Code - Cylinder 7 Glow Plug Control Circuit Low Voltage

What does this mean?

What are the Possible Causes of the DTC P068C 2015 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 P068C 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 P068C 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 P068C 2015 GMC Sierra code?

Need more information on how to fix the P068C 2015 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P068C 2015 GMC Sierra code diagnosed by a professional: Find a repair shop in your area

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P068C 2015 GMC Sierra Code

1. What are the common symptoms of OBDII code P068C in a 2015 GMC Sierra related to Cylinder 7 Glow Plug Control Circuit Low Voltage?

The common symptoms include rough idling, loss of engine power, decreased fuel efficiency, and the illumination of the Check Engine Light.

2. What are the possible causes of OBDII code P068C in a 2015 GMC Sierra indicating an issue with the Cylinder 7 Glow Plug Control Circuit?

Possible causes include a faulty glow plug, damaged wiring or connectors in the glow plug circuit, a malfunctioning glow plug control module, or issues with the vehicle's ECM.

3. How can I diagnose the Cylinder 7 Glow Plug Control Circuit Low Voltage issue in my 2015 GMC Sierra triggering OBDII code P068C?

Diagnosis involves checking the glow plug resistance, inspecting the wiring and connectors for any damage, testing the glow plug control module, and scanning the ECM for any related fault codes.

4. Can I still drive my 2015 GMC Sierra with OBDII code P068C related to Cylinder 7 Glow Plug Control Circuit Low Voltage?

While it may be possible to drive the vehicle with this code, it is not recommended as it can lead to further engine damage and decreased performance. It is best to address the issue promptly.

5. How can I reset the Check Engine Light after repairing the Cylinder 7 Glow Plug Control Circuit Low Voltage problem in my 2015 GMC Sierra?

You can reset the Check Engine Light using an OBDII scanner or by disconnecting the vehicle's battery for a few minutes. However, the light will only stay off if the underlying issue has been successfully resolved.

6. Is it necessary to replace all glow plugs when addressing OBDII code P068C in my 2015 GMC Sierra?

While it is not always necessary to replace all glow plugs, it is recommended to inspect all of them during the diagnostic process to ensure they are functioning properly. Replacing only the faulty ones may be sufficient.

7. Can a DIY enthusiast repair the Cylinder 7 Glow Plug Control Circuit Low Voltage issue causing OBDII code P068C in a 2015 GMC Sierra?

DIY enthusiasts with experience in automotive repair and the necessary tools may be able to address this issue themselves. However, it is advisable to consult a professional mechanic for accurate diagnosis and repair if unsure.

8. How much does it typically cost to repair OBDII code P068C related to Cylinder 7 Glow Plug Control Circuit Low Voltage in a 2015 GMC Sierra?

The cost of repair can vary depending on the underlying cause of the issue, the extent of the damage, and the labor rates in your area. It is recommended to obtain quotes from different mechanics for an accurate estimate.

9. Will ignoring OBDII code P068C in my 2015 GMC Sierra lead to further engine problems?

Ignoring this code can lead to more severe issues such as poor engine performance, increased emissions, and potential damage to other engine components. It is best to address the problem as soon as possible to prevent further damage.

10. Can extreme weather conditions affect the Cylinder 7 Glow Plug Control Circuit and trigger OBDII code P068C in a 2015 GMC Sierra?

Extreme cold weather can put additional strain on the glow plug system, potentially leading to issues with the glow plug control circuit. Ensuring the glow plug system is in good condition can help prevent problems in harsh weather conditions.