P0682 Glow Plug Circuit DTC, Cylinder No. 12

P0682 – OBD-II Trouble Code Technical Description

Cylinder No. 12 Glow Plug Circuit

What does the fault code mean P0682?

This diagnostic trouble code (DTC) P0682 is a universal transmission code that applies to all makes and models of vehicles from 1996 onward. The code indicates a malfunction in the glow plug circuit of cylinder No. 12. The glow plug plays an important role in diesel engines by providing the necessary heating for starting in cold conditions. If the cylinder #12 glow plug does not heat up, it may cause starting problems and loss of power.

To solve the problem, you should diagnose and repair the fault in the glow plug circuit. It is also important to note that other glow plug-related fault codes may also appear with this problem, such as P0670, P0671, P0672 and others.

To accurately diagnose and resolve the problem, it is recommended that you contact a car repair specialist or an authorized dealer, as the specific repair steps may vary slightly depending on the car model.

Possible reasons

Reasons for the P0682 trouble code may include:

1. Faulty glow plug for cylinder No. 12.
2. Open or shorted glow plug circuit.
3. Damaged wiring connector.
4. The glow plug control module is faulty.
5. Shorted or loose wiring, connections or connectors in the preheat circuit.
6. Faulty glow plugs, glow plugs, timers or modules.
7. Blown fuses.

When diagnosing and repairing this problem, the mechanic must consider the above causes one by one, starting with the most likely ones, to find and solve the problem.

What are the symptoms of a fault code? P0682?

If just one glow plug fails, in addition to the check engine light, symptoms will be minimal since the engine will usually start with one faulty plug. This is especially true in frosty conditions. Code P0682 is the main way to identify such a problem. When the engine control computer (PCM) sets this code, the engine will be difficult to start or may not start at all in cold weather or after being parked for a long period of time. The following symptoms are also possible:

• Lack of power before the engine warms up.
• Possible misfires.
• Exhaust smoke may contain more white smoke.
• The engine noise may be unusually loud during startup.
• The preheat indicator may remain active longer than usual.

How to diagnose a fault code P0682?

To fully diagnose and resolve trouble code P0682, you will need a digital volt-ohm meter (DVOM) and an OBD code scanner. Follow these steps:

1. Disconnect the wire connector from the cylinder #12 glow plug and use a DVOM to check the resistance of the plug. The normal range is 0,5 to 2,0 ohms. If the resistance is outside this range, replace the glow plug.
2. Check the resistance of the wire from the spark plug to the glow plug relay bus on the valve cover. To do this, use a DVOM and make sure the resistance is within acceptable limits.
3. Inspect the wires for damage, cracks, or missing insulation. If problems are found with wiring, connectors, or components, replace them.
4. Connect an OBD code scanner to the port under the dash and read stored codes and freeze frame data for additional diagnostics.
5. Check for a faulty glow plug connector using a DVOM while the glow plug heater light is on. Make sure there is a reference voltage and a ground signal at the connector.
6. Check the resistance of potentially faulty glow plugs using a volt-ohmmeter and compare the results to the manufacturer's specifications.
7. Check the fuses to make sure they haven't blown.
8. Check the glow plug relay, timer and module for faults, comparing the results to manufacturing specifications.
9. If all wiring, connectors and components are checked and operating normally, test the PCM using a digital volt-ohmmeter to determine the circuit resistance.
10. Once you have corrected the problems found and replaced the faulty components, clear the error code and recheck the glow plug system to ensure the code does not return.

This approach will help you correctly diagnose and resolve the P0682 trouble code.

Diagnostic errors

Common mistakes when diagnosing a P0682 code include incomplete system testing and unnecessary replacement of relays and spark plug timers, even if they are functioning properly. This may result in an incorrect diagnosis and an error code being returned. It is important to ensure that the entire circuit, including wiring, connectors and components, has been thoroughly inspected before replacing any parts.

How serious is the fault code? P0682?

Code P0682 can have a serious impact on the vehicle's performance, especially its ability to start correctly. Diesel engines depend on glow plugs to provide the necessary heat to initiate combustion of the fuel in the cylinders. If this process is disrupted by faulty glow plugs, it can cause starting difficulties, especially on cold days. In addition, the vehicle may operate less efficiently and as a result, some fuel may remain unburnt, resulting in increased white smoke coming from the exhaust system. Therefore, code P0682 should be taken seriously and should be promptly diagnosed and repaired.

What repair will help eliminate the code? P0682?

To resolve the problem associated with the P0682 code, the mechanic must perform the following repair steps:

1. Replace all damaged cables, connectors and components in the glow plug circuit.
2. If the glow plug connector is faulty, replace it.
3. Replace any defective glow plugs.
4. If the timer, relay or glow plug module is faulty, replace it.
5. If the PCM is faulty, replace it after reprogramming the new module.
6. Replace all blown fuses, as well as identify and eliminate the cause of the burnout.

Effective troubleshooting of the glow plug system will restore normal engine operation and avoid starting problems, especially in cold weather conditions.

What is P0682 Engine Code [Quick Guide]