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Engine-Codes – GMC – P068D GMC

P068D GMC Code - Cylinder 7 Glow Plug Control Circuit High Voltage

Quick Answer

The P068D diagnostic trouble code (DTC) for GMC vehicles specifically indicates an issue with the cylinder 7 glow plug control circuit, where the voltage is detected to be higher than normal. Common causes include A faulty glow plug in cylinder 7, Short circuit in the glow plug control circuit, Damaged wiring harness leading to cylinder 7. 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 GMC indicates Cylinder 7 Glow Plug Control Circuit High Voltage.
Common causes
Common causes include A faulty glow plug in cylinder 7, Short circuit in the glow plug control circuit, Damaged wiring harness leading to cylinder 7.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 12, 2024
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Code P068D GMC Description

The P068D diagnostic trouble code (DTC) for GMC vehicles specifically indicates an issue with the cylinder 7 glow plug control circuit, where the voltage is detected to be higher than normal. Glow plugs are crucial components in diesel engines, as they help heat up the combustion chamber to facilitate cold starts. When the control circuit for the glow plug in cylinder 7 is experiencing high voltage, it can lead to various performance issues in the vehicle.

OBDII Code P068D GMC - Cylinder 7 Glow Plug Control Circuit High Voltage
P068D GMC Code - Cylinder 7 Glow Plug Control Circuit High Voltage

Common Causes of P068D GMC

  1. A faulty glow plug in cylinder 7.
  2. Short circuit in the glow plug control circuit.
  3. Damaged wiring harness leading to cylinder 7.
  4. Malfunctioning glow plug control module.
  5. Corrosion or poor connections in the electrical system.

Symptoms of P068D GMC

  1. Difficulties starting the engine, especially in colder temperatures.
  2. Rough idling or misfiring of the engine.
  3. Decreased fuel efficiency.
  4. Illumination of the check engine light on the dashboard.
  5. Increased exhaust emissions.

How to Fix P068D GMC

  1. Diagnose the issue by using a scan tool to confirm the P068D code and pinpoint the exact cause.
  2. Inspect the glow plug in cylinder 7 and test its functionality.
  3. Check the wiring harness and connections for any damage or corrosion, repairing or replacing as needed.
  4. Test the glow plug control module for proper operation and replace if faulty.
  5. Clear the DTC and test drive the vehicle to ensure the issue has been resolved.

Cost to Fix P068D GMC

The typical repair costs for addressing a P068D code in a GMC vehicle can vary depending on the specific cause of the issue. On average, the parts required for this repair, including a new glow plug, wiring harness, or control module, could range from $100 to $500. Labor costs at an auto repair shop may add another $100 to $300 to the total bill. Keep in mind that these estimates are general guidelines, and actual costs may differ based on the factors mentioned earlier. It's recommended to consult with a qualified mechanic or service center for a more accurate cost assessment.

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Information for Specific GMC Models

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 P068D GMC Code

1. What does the OBDII code P068D mean on a GMC vehicle?

P068D on a GMC indicates a high voltage issue in the Cylinder 7 Glow Plug Control Circuit, which is responsible for controlling the glow plug in that cylinder for optimal combustion during cold starts.

2. What are common symptoms of the P068D code?

Common symptoms include difficulty starting the engine in cold weather, a rough idle, reduced fuel efficiency, and an illuminated check engine light.

3. What causes the P068D code to appear?

The code can be triggered by a faulty glow plug in cylinder 7, damaged wiring or connectors in the glow plug circuit, a malfunctioning glow plug control module, or corrosion on electrical contacts.

4. Can I drive my GMC with the P068D code active?

While you can typically drive with this code, it is not recommended as it can lead to harder starts in cold conditions and may cause long-term damage to the engine or emissions system.

5. How do I diagnose the P068D code on my GMC?

Diagnosis involves inspecting the glow plug in cylinder 7, checking the wiring and connectors for damage or corrosion, and testing the glow plug control module for proper operation.

6. How do I fix the P068D code on my GMC?

Repairs may include replacing the faulty glow plug, repairing or replacing damaged wiring or connectors, cleaning corroded contacts, or replacing the glow plug control module if it is defective.

7. What tools are needed to troubleshoot the P068D code?

You’ll need an OBDII scanner, a multimeter to check electrical continuity, and possibly a torque wrench to remove and install the glow plug.

8. How much does it cost to fix the P068D code on a GMC?

The repair cost varies but typically ranges from $100 to $300, depending on whether the issue is with the glow plug itself or requires more extensive repairs such as module replacement.

9. Can a weak battery cause the P068D code?

Yes, a weak or failing battery can sometimes cause voltage-related issues that may trigger the P068D code, as the glow plug system relies on consistent electrical power.

10. Will clearing the P068D code fix the problem?

Clearing the code will reset the check engine light, but the underlying issue causing the high voltage in the glow plug circuit must be addressed to prevent the code from returning.

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