P0676
UniversalThe Powertrain Control Module (PCM) has detected an abnormal voltage or resistance reading in the glow plug circuit for cylinder 6.
Medium SeverityThis code indicates a malfunction in the glow plug electrical circuit for cylinder 6, which is essential for heating the combustion chamber in diesel engines. Drivers may experience difficulty starting the engine, particularly in cold weather, and a rough idle immediately after starting.
⚠️ Before You Begin (Safety First)
Always ensure the engine is completely cool before attempting any work. Disconnect the battery before inspecting or replacing electrical components to prevent accidental shorts or injury. Use proper eye protection and gloves.
Common Symptoms
- Hard start in cold weather
- Rough idling immediately after cold start
- Check Engine Light illuminated
- White smoke from exhaust during cold start (briefly)
Common Causes
- Faulty or burned out glow plug (cylinder 6)
- Open or short in the glow plug wiring harness
- Corroded or loose electrical connector
- Defective glow plug control module/relay
Frequently reported on: Ford F-Series Super Duty (6.0L, 6.4L, 6.7L Power Stroke), Ram 2500/3500 (Cummins 6.7L), Chevrolet Silverado/GMC Sierra 2500/3500 (Duramax 6.6L), Mercedes-Benz Sprinter (Diesel engines)
Diagnostic Steps
- Visually inspect the wiring and connector to the cylinder 6 glow plug for damage or corrosion.
- Test the resistance of the cylinder 6 glow plug using a multimeter; compare to manufacturer specifications.
- Test for voltage at the glow plug connector during cold start (or when glow plug system is active).
- If the glow plug is faulty, carefully remove and replace it.
- Clear the DTCs and test drive the vehicle.
👨🔧 When to Call a Professional
If you encounter significant resistance when trying to remove the glow plug or if it appears stuck or stripped, stop immediately and consult a professional mechanic. Forcing it can cause the glow plug to break off in the cylinder head, leading to a much more costly repair.
Commonly Asked Questions
Can I drive with a P0676 code?
Yes, but it may be difficult to start, especially in cold weather, and could lead to increased emissions or unburnt fuel. It's best to address it promptly.
How do I test a glow plug?
You can test its resistance with a multimeter (should be low, typically less than 1 ohm) or check for continuity to ground. Some technicians also perform a current draw test.
Is it okay to replace just one glow plug?
While possible, it's often recommended to replace all glow plugs on one bank or even all of them if they are old, as others may fail soon due to similar wear.
What is the glow plug control module?
It's an electronic unit that controls the timing and duration of power supplied to the glow plugs. A fault here can also trigger P0676 if it's not supplying power correctly to cylinder 6, even if the glow plug itself is good.