P0681 Cylinder 11 Glow Plug Circuit

P0681 code definition

A P0681 code means that the powertrain control module sensed a problem in the glow plug circuit for the engine cylinder #11. However, this code is often recorded along with other glow plug circuit codes, and it is important to repair them in the order received.

What the P0681 code means

P0681 is an OBD-II generic code that appears when a variation in the voltage exceeds 10% of the manufacture's specifications. This is a code that will appear strictly in vehicles with diesel engines as the glow plugs are used to pre-heat the engine's cylinders to allow the diesel fuel to ignite in colder conditions. The glow plugs use battery voltage to become heated, and the code is generated if there is a problem in cylinder 11's plug function.

What causes the P0681 code?

The P0681 code is caused by:

• Defective glow plug
• Defective glow plug relays
• Faulty timer or module in the glow plug
• Shorted or open circuit
• Electrical flaws in the circuit for the glow plug
• Blown fuse (though the cause of the blown fuse must first be detected)

What are the symptoms of the P0681 code?

When the P0681 code appears, it is often accompanied by such symptoms as the glow plug indicator on the dash, difficulty getting the engine to start, heavy white smoke and/or increased noise at start up, misfiring of the engine, and the check engine indicator.

How does a mechanic diagnose the P0681 code?

To diagnose the P0681 code, the mechanic or technician must use the OBD-II scanner and verify the information. They will need to clear the code and retest the vehicle, and use the freeze frame data to determine the order in which codes have recorded as this is important in dealing with glow plug issues, which may occur in multiples.

The technician examines the wiring and connections, making repairs are needed and then tests for the codes. The individual glow plug is tested for voltage and replaced if needed. Fuses are also tested with the heater activated and replaced if needed. System circuitry is also tested, and the relay, timer and module are also tested with any components replaced as needed.

Common mistakes when diagnosing the P0681 code

It is a common mistake for the technician to replace the glow plug relays and timers prior to diagnosing and testing the system. They should test connections, glow plugs and wiring before making any repairs.

How serious is the P0681 code?

Though the P0681 code alone may not prevent the vehicle from operating, if there are multiple glow plug codes, it is indicative of a serious problem. It could leave the vehicle in a no-start or low performance condition, especially in cold weather.

What repairs can fix the P0681 code?

The P0681 code can be dealt with using the following repairs:

• Checking the codes and attempting to repair any other faulty glow plugs before the #11 cylinder
• Performing a visual inspection of the wiring and connections, repairing anything showing signs of damage or defect
• Checking the #11 glow plug connection and using a digital ohm meter to measure the voltage and testing the ground signal. Replacing the glow plug if voltage and ground are present.
• Testing and replacing fuses in the heater or testing system circuitry if fuses blow once replaced
• Testing and replacing the timer or relay and/or module if needed and making any electrical repairs
• PCM replacement should not be needed, but could be the issue

Additional comments for consideration regarding the P0681 code

There is usually no issue with the PCM, though it is not impossible. This is the last item to test if all of the diagnostics and tests of the #11 cylinder glow plug reveal no reason for the code to have appeared.

Need help with a P0681 code?

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