The P0674 code refers to a failure of the glow plug in cylinder number 4 in a diesel engine. Glow plugs are essential for helping to start a diesel engine when it is cold. They heat up quickly to increase the temperature in the combustion chamber, allowing the fuel to ignite by compression.
Explanation of code P0674:
When the diesel engine is cold, the compression engine generates extremely high temperatures that can be lost quickly due to the cold cylinder head. To solve this problem, diesel engines are equipped with glow plugs that heat the combustion chamber before starting.
The P0674 code indicates that the glow plug in cylinder number 4 is not working properly. This can lead to difficulties starting the engine, especially in cold weather.
Possible symptoms:
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Difficulty starting when cold or after a long period of non-use (especially in cold weather).
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Lack of power until the engine warms up.
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Hesitation or misfires during acceleration.
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The glow plug indicator light does not turn off, indicating a problem with the preheating.
Possible causes:
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Faulty glow plug in cylinder number 4.
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Damaged wiring or connectors in the glow plug circuit.
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Faulty relay or control module for the glow plug.
Diagnostic and repair steps:
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Test the glow plug in cylinder number 4 with a digital ohmmeter:
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Disconnect the glow plug connector.
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Use the ohmmeter to measure the resistance between the glow plug terminal and a good ground. The resistance should be between 0.5 and 4.0 ohms (specific values may vary depending on the vehicle model).
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If the resistance is outside this range, the glow plug must be replaced.
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Check the wiring and connectors:
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Check the glow plug wires for any short circuit, disconnected wire, wear, or deterioration.
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Also inspect the fuses and relays associated with the glow plug system.
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Test the glow plug relay:
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Check the relay by ensuring it provides adequate current to the glow plugs.
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Clear the codes and test:
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Use an OBD scanner to clear the code once repairs are completed and test the system to check if the problem persists.
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Recommended repair:
If the glow plug in cylinder number 4 is faulty, it must be replaced. If the problem comes from the wiring or connectors, these must be repaired or replaced. In case of a problem with the relay or control module, these will also need to be replaced.
Importance of diagnosis:
A glow plug failure can make starting difficult, especially in cold weather, and affect engine performance until it is completely warmed up. It is important to resolve this issue to avoid further engine damage and ensure its proper operation.