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P0673 OBD-II Trouble Code: Cylinder 3 Glow Plug Circuit

Check Engine Light

P0673 Code Definition

The P0673 code is a generic powertrain code related to issues with a computer output circuit. In this case, it means that an issues has been noted with the glow plug circuit in cylinder 3 of your engine.

Codes related to the P0673 include:

What the P0673 Code Means

A glow plug is a device utilized in diesel engines to heat a cylinder head when starting up a cold engine. The diesel engine uses the high level of heat through compression, which quickly ignites the fuel. Each cylinder of the engine has a glow plug to heat the cylinder head.

When a P0673 trouble code is stored, it means that the system reference voltage allowed by the vehicle’s engine control module (ECM) has exceeded 10% of preset variance parameters.

While a glow plug will typically last 100,000 miles, they can fail before that mileage. The glow plug is installed in the cylinder head as close as possible to the cylinders combustion point. Using oil and transmission sensors, the ECM will determine if the glow plug is needed for ignition and grounds the glow plug timer module, which grounds the glow plug relay. Typically, a P0673 code means the glow plug has failed to heat up and could be damaged.

What Causes the P0673 Code?

Several problems may cause a P0673 code including:

  • Damaged or defective glow plug in cylinder 3
  • Damaged or defective glow plug module or timer
  • Damaged or defective glow plug relay
  • Blown fuse(s)
  • Damaged, defective, corroded or loose wiring, harnesses, and related connectors n the glow plug circuit

What are the Symptoms of the P0673 Code?

Symptoms of a P0673 code may include:

  • An illuminated warning or check engine light
  • Vehicle may not start up as quickly as normal
  • Vehicle may not start at all in cold weather
  • Glow plug indicator light may not illuminate or illuminate longer than normal
  • Additional white smoke when the vehicle starts
  • Vehicle may have a loss in power
  • Abnormal, loud noise from the engine
  • The engine may misfire

How Does a Mechanic Diagnose the P0673 Code?

A mechanic may use several methods to diagnose a P0673 trouble code, including:

  • Test glow plug timer, relay, or module

  • Utilize an OBD-II scanner to check for a stored P0673 trouble code

  • Check if glow plug will “warm” with battery voltage or test with digital volt/ohmmeter

  • Test all system fuses to ensure they are in working order with the glow plug heater activated

  • Test the glow plug after disconnecting it from cylinder 3 and check ground and resistance

  • Visually inspect wiring, harnesses, and connectors related to the glow plug circuit for damage

Common Mistakes when Diagnosing the P0673 Code

If blown fuses are located, there may be an underlying problem beyond what a P0673 code holds, so it is always recommended to repair stored codes in the order in which they appear. Often, glow plug timers and relays are replaced before wiring and the glow plug itself is tested, which can lead to misdiagnosis and unnecessary repairs.

How Serious is the P0673 Code?

Because a vehicle’s safe driving operation may be impacted due to faults that store a P0673 code, this code is considered a potentially serious code. When this code appears, it is recommended to immediately take your vehicle to your local service center or mechanic for repair and diagnosis.

What Repairs can Fix the P0673 Code?

Several repairs can fix a P0673 trouble code and include:

Additional Comments for Consideration Regarding the P0673 Code

Often, additional glow plug circuit codes will accompany a P0673, so it is recommended to do a full diagnosis and note all trouble codes that may be stored to fully repair the issue.

Need Help with a P0673 Code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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