P0680 OBD-II Trouble Code: Cylinder 10 Glow Plug Circuit

Check Engine Light

P0680 Code definition

The P0680 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 10 of your engine.

Codes related to the P0680 include:

What the P0680 code means

Used in diesel engines to heat a cylinder head when starting up a cold engine, the glow plug is an integral part of cold weather start-up in a diesel-powered vehicle. The diesel engine uses the high level of heat through compression, which then quickly ignites the fuel. 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 approximte mileage.

When a P0680 trouble code is stored, the system reference voltage allowed by the vehicle’s engine control module (ECM) has exceeded 10% of the allowed variance.

The glow plug is installed in the #10 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 P0680 code means the glow plug for cylinder 10 has failed to heat up and could be damaged or faulty.

What causes the P0680 code?

Several problems may cause a P0680 code including:

  • Damaged or defective glow plug in cylinder 10
  • Damaged or defective glow plug module or timer
  • Replace the glow plug relay
  • May have blown a fuse(s)
  • Damaged, defective, corroded or loose wiring, harnesses, and related connectors in the glow plug circuit for cylinder 10

What are the symptoms of the P0680 code?

Symptoms of a P0680 code may include:

  • An illuminated warning or check engine light
  • Vehicle may start up more slowly than normal
  • Vehicle may not start at all in cold weather
  • Glow plug indicator light may not illuminate or may illuminate longer than normal
  • There may be an unusual amount of white smoke when the vehicle starts
  • A possible loss in overall vehicle power
  • Abnormal, loud noise may be heard coming from the engine
  • The engine may misfire

How does a mechanic diagnose the P0680 code?

A mechanic may use several methods to diagnose a P0680 trouble code, including:

  • Utilize an OBD-II scanner to check for a stored P0680 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 10 and check ground and resistance

  • Check if glow plug for cylinder 10 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 glow plug timer, relay, or module

Common mistakes when diagnosing the P0680 code

If blown fuses are located, there may be an underlying problem beyond what a P0680 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 P0680 code?

Because a vehicle’s safe driving operation may be impacted due to faults that store a P0680 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 P0680 code?

Several repairs can fix a P0680 trouble code and include:

Additional comments for consideration regarding the P0680 code

Often, additional glow plug circuit codes will accompany a P0680, 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 P0680 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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