P0676 — Cylinder 6 Glow Plug Circuit/Open #

Note: The code title may vary depending on the vehicle manufacturer. Below are common variations found in OEM documentation:

• Cylinder 6 Glow Plug Circuit/Open — Generic/SAE
• Glow Plug Circuit Malfunction, Cylinder 6 — Ford
• Heater Plug 6 Control Circuit/Open — Mercedes-Benz
• Cylinder 6 Glow Plug Circuit (Open) — GM
• Glow Plug 6/Open Circuit — Dodge/RAM

Summary of Code P0676 #

P0676 is a diagnostic trouble code (DTC) that indicates the powertrain control module (PCM) has detected an open circuit or malfunction in the glow plug circuit for cylinder 6. Glow plugs are heating elements used in diesel engines to warm the air in the combustion chamber for easier cold starting. This code is most often triggered when the PCM senses that the voltage or resistance in the glow plug circuit for cylinder 6 is outside the expected range, typically due to an open circuit or failed component.
If this code appears, it usually means that cylinder 6’s glow plug is not heating as it should, which can cause starting issues and rough running, especially in cold conditions. While the engine may still run, performance and reliability could be affected, particularly during cold starts.

Frequent Symptoms for Code P0676 #

When P0676 is set, you may notice symptoms particularly during engine startup or in colder weather. The severity depends on how many cylinders are affected and how cold the ambient temperature is. Here are common signs:

• Hard starting when the engine is cold
• Rough idle after a cold start
• Noticeable white smoke from the exhaust during startup
• Check Engine Light illuminated
• Reduced engine performance until the engine warms up

Likely Causes for Code P0676 #

P0676 is most commonly caused by electrical issues in the glow plug circuit for cylinder 6. The list below orders the causes from most to least frequent:

1. Failed glow plug on cylinder 6 (burned out or open circuit)
2. Faulty glow plug wiring or connector (corrosion, loose, or broken wire)
3. Bad glow plug control module or relay (not sending voltage to the plug)
4. Poor ground connection at the cylinder head or glow plug harness
5. Faulty PCM (rare, but possible if everything else checks out)

Step-by-Step Diagnosis for Code P0676 #

Accurate troubleshooting prevents unnecessary parts replacement. Follow this sequence to pinpoint the issue:

1. Read all stored and pending codes with a scan tool and note freeze-frame data.
2. Visually inspect the cylinder 6 glow plug, connectors, and related wiring for signs of damage, corrosion, or loose connections.
3. Check resistance of the cylinder 6 glow plug using a multimeter. Most glow plugs should read between 0.5–2.0 ohms (refer to OEM specs).
4. Test for voltage at the glow plug with the key on (engine cold). Lack of voltage could indicate a faulty relay or control module.
5. Inspect the glow plug control module/relay for proper operation and output to cylinder 6.
6. If all above tests pass, check continuity between the PCM and the glow plug circuit harness.
7. If the wiring, plug, and control module are functional, check for PCM faults (rare; consult OEM diagnostic flowchart).

Possible Repairs for Code P0676 #

Once the root cause is identified, apply the appropriate fix. Here are repairs commonly performed for this code:

• Replace the cylinder 6 glow plug if resistance is out of spec or it fails the voltage test.
• Repair or replace damaged wiring or connectors in the glow plug circuit.
• Replace the glow plug control module or relay if it’s not functioning or supplying voltage.
• Clean or repair ground connections to ensure proper circuit completion.
• Replace the PCM only if all other components check out and the issue persists (rare).

Can You Drive with Code P0676? #

Yes, but with limitations. Your vehicle will usually run with a single glow plug circuit fault, but you may experience hard starting, rough idle, and increased exhaust smoke—especially in cold weather. Prolonged driving with this code can lead to excessive engine wear due to poor cold combustion and increased emissions. It’s best to address the issue as soon as possible to maintain performance and prevent further complications.

Vehicles Most Commonly Affected by Code P0676 #

This code is prevalent in diesel-powered vehicles, particularly those using individual glow plug monitoring. The following makes and models are frequently affected:

• Ford Super Duty (F-250, F-350) Power Stroke Diesel
• Chevrolet Silverado/GMC Sierra Duramax Diesel
• Dodge/RAM Cummins Diesel
• Mercedes-Benz Sprinter
• Volkswagen TDI engines

Common Mistakes & Best Practices for Code P0676 #

Technicians and DIYers sometimes overlook key steps when diagnosing or repairing P0676. Avoid wasted time and expense by following these best practices:

• Replacing all glow plugs without confirming which one is faulty (not all glow plugs fail at once).
• Ignoring wiring and connector inspections—many issues are due to simple corrosion or loose connectors.
• Not checking the control module/relay when voltage is missing at the glow plug.
• Skipping resistance tests—always confirm a glow plug is actually bad before replacing.
• Clearing the code without fixing the root cause—the code will return if the fault remains.

FAQ Express: P0676 #

Have quick questions about this code? Here are direct answers:

• Q: Will P0676 cause my engine to misfire?
  A: Not typically, but it can cause rough idle and hard starting, which might feel similar to a mild misfire during cold starts.
• Q: Can I replace just one glow plug, or should I do all of them?
  A: You can replace just the faulty glow plug. However, if others are old or have high mileage, consider replacing all as preventative maintenance.
• Q: Does this code mean my engine will not start at all?
  A: Usually, the engine will still start, especially in warm climates. In colder conditions, starting may be difficult or require multiple attempts.