P0682Generic code

P0682 Code: Glow Plug 12 Circuit

The P0682 code means the glow plug for cylinder 12, or its circuit, is not working the way the computer expects. A diesel with this fault starts harder when cold and puffs white smoke for the first few minutes. It is a low severity code and you can keep driving, but cold starts will get worse.

Severity
Low
Can I keep driving?
Yes, no immediate risk
Estimated cost
$20 to $300
Difficulty
Medium
System
Ignition and Misfires
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the P0682 code means

The glow plug control module feeds each glow plug separately and watches the current each one draws. If the cylinder 12 plug draws no current (a burned out plug or a broken wire) or draws too much (a short), the module reports it to the computer, which stores the P0682 code.

With one burned out glow plug the engine usually still starts, but it cranks longer when cold and runs with white smoke and extra noise until it warms up. With several burned out plugs, the engine may not start at all on a winter morning.

Glow plugs can snap off when you remove them, especially in aluminum cylinder heads. Warm the engine first, soak the plug with penetrating oil and give it time to work, and use the correct torque. If one does break off, there are specialty extraction tools made for the job.

The manufacturer decides how cylinders are numbered, so confirm which one is cylinder 12 in the service manual before you start pulling parts.

P0682 code symptoms

  • Hard starting when the engine is cold.
  • White smoke at startup.
  • Rough idle when cold.
  • Glow plug light or check engine light on.

Likely causes of the P0682 code

  1. Burned out cylinder 12 glow plug. The element reads infinite resistance.
  2. Loose or burned glow plug connector or wire, damaged by engine heat.
  3. Damaged glow plug module output, often caused by a plug that is shorted.
  4. Shorted glow plug. The element reads close to zero resistance.

How to diagnose the P0682 code step by step

  1. Measure the resistance of glow plug 12. As a rough guide it should be 0.5 to 2 ohms, and an infinite reading means the plug is burned out.
  2. Compare it with the other glow plugs. A plug that reads very different from the rest is the suspect.
  3. Check the voltage at its connector during preheat. It should be battery voltage.
  4. Inspect the wire and the connector for heat damage, corrosion and loose pins.

How to fix the P0682 code

  • Replace the glow plug. It makes sense to replace all of them if the engine has a lot of miles on it.
  • Repair the connector or the wire.
  • Replace the module if its output is damaged.
  • Clear the code and verify the repair on a cold start.

Technical reference data

  • Glow plug resistance: 0.5 to 2 ohms.
  • Initial draw per glow plug: 8 to 15 amps.
  • Typical tightening torque: 8 to 20 N·m (about 6 to 15 lb-ft).
  • Reference values only: check the manufacturer data for your vehicle.

Brand-specific notes

On Volkswagen TDI, Ford Power Stroke 6.0 and 6.4, and Mercedes CDI engines, the module identifies the specific glow plug that has the fault, so the P0682 code points you to a single cylinder.

P0682 on Ford

Glow plugs that break off in the cylinder head are a known problem on the Ford Power Stroke, so take your time and use the right extraction approach when you remove them.

Frequently asked questions about P0682

What does the P0682 code mean?
It means the glow plug for cylinder 12, or the wiring that feeds it, is not working. The module either sees no current (burned out plug or broken wire) or too much current (a short).
Can I drive with a P0682 code?
Yes. The problem is mostly cold starting, so the engine will run normally once it is warm. Do not ignore it going into winter, because a second or third bad plug can leave you stranded.
Do I replace just one glow plug?
If the other plugs have a lot of miles on them, it is smart to replace the whole set. They wear at about the same rate, and removing them again later costs labor twice.
Can a glow plug break when I take it out?
Yes, it can. Do the job with the engine warm, soak the threads with penetrating oil first and use the correct torque. A broken plug needs a specific extraction tool.
How much does it cost to fix P0682?
Expect roughly $20 to $300 per glow plug including labor, depending on the engine and how hard the plug is to reach.

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