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P0676 OBD-II Trouble Code: Cylinder 6 Glow Plug Circuit

Check Engine Light

P0676 Code Definition

The P0676 code is a generic powertrain code related to issues with a computer output circuit. In this case, it means that an issue has been noted with the glow plug circuit in cylinder 6 of a vehicle’s engine.

Codes related to the P0676 include:

What the P0676 Code Means

Used in diesel engines to heat a cylinder head when starting up a cold engine, the glow plug is an important part of cold weather start-up. Each cylinder of the engine has a glow plug to heat the cylinder head. A glow plug will typically last 100,000 miles, but can fail before that approximate mileage. The diesel engine uses the high level of heat through compression, which quickly ignites the fuel.

When a P0676 trouble code is stored, the system reference voltage allowed by the vehicle’s engine control module (ECM) has exceeded 10% of preset variance parameters in cylinder 6.

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. This is usually used on a cold start. Typically, a P0676 code means the glow plug for cylinder 6 has failed to heat up properly and could be damaged.

What Causes the P0676 Code?

Several problems may cause a P0676 code including:

  • Damaged or defective glow plug in cylinder 6
  • Damaged or defective glow plug module or timer
  • Damaged or defective glow plug relay
  • Possible blown fuse(s)
  • Damaged, defective, corroded or loose wiring, harnesses, and related connectors in the glow plug circuit for cylinder 6

What are the Symptoms of the P0676 Code?

Symptoms of a P0676 code may include:

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

How Does a Mechanic Diagnose the P0676 Code?

A mechanic may use several methods to diagnose a P0676 trouble code, including:

  • Utilize an OBD-II scanner to check for a stored P0676 trouble code

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

  • Test the glow plug after disconnecting it from cylinder 6 and check ground and resistance

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

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

  • Test glow plug timer, relay, or module

Common Mistakes when Diagnosing the P0676 Code

If blown fuses are located, there may be an underlying problem beyond what a P0676 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 P0676 Code?

Because a vehicle’s safe driving operation may be impacted due to faults that store a P0676 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 P0676 Code?

Several repairs can fix a P0676 trouble code and include:

Additional Comments for Consideration Regarding the P0676 Code

Often, additional glow plug circuit codes will accompany a P0676, so it is recommended to do a full diagnosis and note all trouble codes that may be stored to fully repair the issue. Ensure that codes are handled in the order they appear on the scanner.

Need Help with a P0676 Code?

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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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