P0674 - GLOW PLUG, CYLINDER 4 - CIRCUIT MALFUNCTION

In gasoline engines, spark plugs burn the fuel. In the case of diesel engines, although they do not use spark plugs because the fuel is burned by compression, they have glow plugs that play a very important role in a cold climate.

These glow plugs not only increase the temperature of the diesel engine during cold weather or after long periods of engine inactivity but also reduce engine emissions. The glow plugs heat the cylinder head for a few seconds to bring the engine to normal operating temperature.

When a malfunction occurs in the number 4 glow plug circuit, the DTC P0674 OBD2 code is set because the PCM (Powertrain Control Module) has observed that the reference voltage of this glow plug circuit has varied at least 10% over the manufacturer’s specifications.

• Check Engine light ON.
• The glow plug malfunction light remains on.
• Misfiring.
• Problems starting the engine especially during cold weather.
• An excessive amount of white smoke is expelled from the exhaust.
• Noticeable engine noises when starting.

Reasons to set the P0674 OBDII diagnostic code:

• The glow plug for cylinder 4 may be faulty.
• Perhaps there is a short in the heater circuit.
• The Cable system connector may be damaged
• The GPCM (Glow Plug Control Module) may be defective.

To troubleshoot faults related to the P0674 OBD2 error code, try this:

• Disconnect the #4 glow plug connector from the plug, and check for 0.5 to 2.0 ohms to the glow plug using a DVOM on the ohm scale. You can replace the glow plug in case it is not within this range.
• Check the resistance of the wire from the spark plug to the relay bus bar. If the resistance value exceeds 2 ohms, replace the spark plug wire.