P0672 Cylinder 2 Glow Plug Circuit

P0672 code definition

The P0672 code is an OBD-II generic code indicating a problem with the cylinder 2 glow plug circuit.

What the P0672 code means

P0672 applies to diesel vehicles and it means that the glow plug in cylinder #2 has failed to produce the high level of heat required to perform a cold start in a diesel engine. All diesels devices to heat the cylinders enough to ignite the fuel when the engine is cold, and this code identifies the #2 glow plug circuit as the problem.

What causes the P0672 code?

You may see this code for several reasons:

• There is a fault in the #2 cylinder glow plug.
• There are damages in the wiring connector.
• There is an open or shorted circuit in the glow plug.
• The control module for the glow plugs is faulty.

What are the symptoms of the P0672 code?

Because the job of the glow plug is to help the diesel engine to turn over in cold weather, the symptoms are often very obvious. However, with a single faulty plug, you may see only a "check engine" light and minimal signs of a problem. In fact, most diesel engines can start with a single faulty plug. When temperatures are below freezing, though, the symptoms may include:

• Hard starts on engines due to a cold block and failed glow plug.
• No start conditions.
• Inadequate power until the engine is fully heated.
• The engine hesitates when attempting to accelerate.
• Engine is missing or skipping in cold weather.
• The pre-heat light continues to remain lit and does not shut off when using the vehicle.

How does a mechanic diagnose the P0672 code?

Mechanics will need to use their DVOM (digital volt ohm meter) to perform the diagnostic tests. Begin by disconnecting wiring to the #2 cylinder glow plug, and placing the DVOM on ohms before touching the red lead to the glow plugs empty terminal and grounding the black lead. The range must be .5 to 2.0 ohms. Next, the mechanic must consider resistance in the glow plug wire and the relay buss bar on the valve cover. This is done by placing the red lead to the buss bar number one wire and the black to the side of the glow plug. The same range of .5 to 2.0 ohms is needed. If it is too high, replace your lead wired to the plug from the buss bar.

Reconnect the wires and visually examine for any signs of cracks or failed insulation. Test with code reader connected to the OBD by turning the key, leaving the engine off and clearing the codes.

Common mistakes when diagnosing the P0672 code

It is not advisable to replace any of the glow plug timers and relays before properly diagnosing the connections. Failing to test wiring and connectors, as well as the glow plugs, easily causes mistakes in the diagnostic process.

How serious is the P0672 code?

The P0672 code will not, usually, prevent a vehicle from starting. If it is only one bad plug, the engine can continue to start. However, over time and changing temperature, the engine may become more and more difficult to start if sitting in cold weather, and this issue can cause a loss in power and acceleration.

What repairs can fix the P0672 code?

The most common repairs needed to fix the P0672 code include:

• Validating the code with a code scanner, resetting codes and road testing the vehicle. If the code reappears, the next step is to do a visual inspection of the wiring.
• Remove and test individual plugs as explained in diagnostics, then move on to testing fuses with the glow plug heater activated to reveal if they break down when under load. Replace fuses as needed and activate the heater. If fuses blow, look at the system circuitry for the heater.
• Alternately, you may have to test the plug relay or module according to the manufacturer's specs. Replacing relays and wires as needed.
• Retesting can indicate normal system functions, meaning that the final repair may be to test circuit resistance between the PCM and the plug module, but PCM issues are rare.

Additional comments for consideration regarding the P0672 code

Voltage in the system exceeding 10% of that suggested by a vehicle's manufacturer will typically cause this code to be stored in the system, and for a check engine light to illuminate.

Need help with a P0672 code?

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