P0682: Glow Plug Circuit Cylinder 12

Introduction

The DTC P0682 trouble code indicates a problem with the glow plug circuit for cylinder 12. This code is common in diesel vehicles equipped with a glow plug ignition system, and can indicate a malfunction that affects engine performance, especially during cold starts. In this article, we will explore the symptoms, causes, diagnostic procedures, and solutions to resolve the issue associated with this code.

Symptoms

Symptoms of a fault associated with DTC code P0682 can vary depending on the severity of the problem. However, the following symptoms are commonly observed:

  • Difficulty starting :
    The engine may have difficulty starting, especially in cold conditions.

  • Excessive exhaust fumes :
    Black or blue smoke may be emitted during operation.

  • Engine light comes on :
    The engine light comes on on the dashboard, indicating the presence of an error code.

  • Engine performance compromised :
    The vehicle may exhibit a loss of power or erratic operation.

  • Irregular heating :
    The engine may heat up unevenly, with the temperature fluctuating.

Cause

The causes of the P0682 code can be multiple and include:

  • Faulty spark plug :
    The glow plug in cylinder 12 may be bad or not working.

  • Wiring problems :
    Damaged wires, shorts, or loose connections in the glow plug circuit can cause problems.

  • Engine control unit (ECU) fault :
    A malfunction of the ECU can prevent the glow plug circuit from functioning properly.

  • Blown fuse :
    A blown fuse protecting the glow plug circuit can cause the glow plug to not fire.

  • Mass problems :
    A bad ground connection can affect the proper functioning of the circuit.

Diagnosis

Diagnosing the P0682 code requires a systematic approach. Here are the steps to follow:

  1. System Scan :
    Use an OBD-II scanner to confirm the presence of DTC code P0682 and check for related codes, such as P0672 (Glow Plug Cylinder 2) or P0673 (Glow Plug Cylinder 3).

  2. Check Engine Light :
    Check if the engine light is on and note any other DTC codes present.

  3. Visual inspection :
    Perform a visual inspection of the glow plug circuit, checking wires, connectors and fuses.

  4. Glow plug check :
    Measure the resistance of the No. 12 cylinder glow plug using a multimeter. It should be within a specific range; values outside of tolerance indicate a bad glow plug.

  5. Engine Control Unit (ECU) Test :
    Check that the engine control unit is sending correct signals to the glow plug circuit.

  6. Ground signal control :
    Make sure all ground connections are secure and free of rust or corrosion.

Resolution and repair

Once you have identified the cause of the P0682 code, you can proceed to its resolution. Here are some strategies:

  • Replacing the spark plug :
    If the glow plug is faulty, it needs to be replaced. Make sure you use quality replacement parts.

  • Wiring Repair :
    If you encounter wiring problems, repair or replace any damaged wires and make sure the connections are secure.

  • Replacing the engine control unit (ECU) :
    If the engine control unit is faulty, it may need to be replaced or repaired.

  • Replacing the fuse :
    If a fuse is blown, replace it with a new one of the same rating.

  • Mass check :
    Clean and repair ground connections to ensure proper operation.

Insight into the components involved

Electrical and Mechanical Components in the Glow Plug Circuit

The glow plug circuit is made up of several key components that work together to ensure the proper functioning of the diesel engine ignition system. These components include:

  • Glow plug :
    These devices heat the air in the cylinder to help ignite the fuel during cold starting attempts. They can be ceramic or metal and their resistance is critical for proper operation.

  • Engine Control Unit (ECU) :
    The ECU controls the glow plug firing by monitoring engine temperature and cranking demands. A malfunction of the ECU can lead to incorrect glow plug firing.

  • Wiring and connectors :
    The wiring harness connects the glow plug to the ECU and must be free of damage or corrosion. The connectors must be tight to ensure proper signal transmission.

  • Fuses :
    Fuses protect the glow plug circuit from overload. It is important to check them regularly and replace them if necessary.

Conclusions

The DTC P0682 trouble code represents a serious problem in the glow plug circuit of cylinder 12, which can potentially affect engine performance, especially during cold start conditions. Through proper diagnosis and a systematic approach to troubleshooting, the problem can be identified and resolved effectively. Preventative maintenance and care of the electrical and mechanical components involved can help avoid future failures and keep your vehicle running smoothly.

Important
Not all OBD2 codes used by one manufacturer are used by other brands, and may not have the same meaning.
The information presented here is for informational purposes only. We are not responsible for any actions you take on your vehicle. If you have any concerns about repairing your vehicle, please contact your repair shop.