P0676 on the LBZ Duramax indicates a fault in the glow plug circuit for cylinder 6. The Duramax relies on glow plugs for clean, easy cold starts, so this code often shows up as cold-start trouble. This guide covers what it means and how to repair it.
What P0676 means
P0676 is defined as Glow Plug Circuit Cylinder 6. The 2006-2007 LBZ Duramax uses individual glow plugs managed by a glow plug control module. The module checks each plug's circuit; when the cylinder 6 circuit reads open, shorted, or out of the expected resistance range, it stores P0676. The code flags the circuit, so the plug, wiring, and module are all candidates.
Common causes
- Failed glow plug on cylinder 6
- Corroded or loose connector at the glow plug
- Damaged or chafed glow plug harness
- Faulty glow plug control module output for that circuit
- High resistance from a poor terminal connection
Symptoms
- Check engine light with stored P0676
- Hard starting in cold weather
- Rough idle or a miss just after a cold start
- White smoke at cold startup
- Longer cranking before the engine catches when cold
How to diagnose it
Measure the resistance of the cylinder 6 glow plug and compare it to the others; a good plug reads low resistance and an open plug reads infinite. Inspect the connector and harness for corrosion or damage and make sure the terminal is clean and tight. If the plug and wiring are good, test the control module's output for cylinder 6. On the LBZ, a single failed plug is the most common cause of an individual-cylinder glow plug code.
How to fix it
Replace the cylinder 6 glow plug if it tests bad, taking care during removal. Repair corroded or damaged wiring and clean the terminal for a solid connection. If the control module output for that circuit has failed, replace the module. After the repair, clear the code, confirm the circuit reads correctly, and verify cold-start quality improves.
Frequently asked questions
Can I drive with P0676?
Usually yes in mild weather, but cold starts will suffer. Fix it before winter to avoid hard starting and white smoke.
How long do LBZ glow plugs last?
They vary, but at higher mileage failures become more common. Replacing the whole set is reasonable if one has already failed.
Do I need a scan tool to confirm P0676?
A scan tool helps read the code and clear it, but you can test the individual plug resistance and wiring with a multimeter.
Need parts or a second opinion? The team at Core Diesel Parts can help you match the right components to your engine. Email sales@coredieselparts.com with your VIN and symptoms and we will point you to the correct parts.
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