The P0676 is an issue with the electrical circuit of the glow plug in cylinder 6. Glow plugs are essential components in diesel engines, providing the necessary heat to ignite the fuel-air mixture in cold conditions. A malfunction in the glow plug circuit can lead to difficulties starting the engine in cold weather, increased emissions, and can even affect the overall performance and fuel efficiency of the vehicle.
P0676 quick overview
| Meaning | P0676 – Cylinder 6 Glow Plug Circuit |
| Is it serious? | Yes, this issue can affect the vehicle’s startability and engine performance, especially in cold weather conditions. |
| Possible causes | – Faulty glow plug in cylinder 6 – Wiring or connector issues in the glow plug circuit – Faulty glow plug control module – Problems with the vehicle’s ECM |
| How to diagnose? | Inspect the glow plug in cylinder 6 for damage or wear and replace if necessary. Check the wiring and connectors for damage, corrosion, or poor connections. Test the glow plug control module for proper operation. Examine the ECM for any signs of issues that could affect its control over the glow plug circuit. Measure the resistance of the glow plug to ensure it falls within the manufacturer’s specifications. |
P0676 Meaning
When a P0676 code appears, it points to a problem with the glow plug in the sixth cylinder of your diesel engine. Glow plugs act like little heaters that warm up the engine’s cylinders so the diesel fuel can ignite more easily when it’s cold outside. If there’s a fault in the circuit—like a bad plug, a broken wire, or even an issue with the engine’s computer (ECM)—it might mean your vehicle will have a hard time starting on chilly mornings or run less efficiently. Fixing the problem could be as straightforward as replacing a worn-out glow plug or as complex as sorting out electrical issues within the circuit.
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How to fix P0676 – learn from mechanics
I looked into P0676 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.
Case #1: Ford
Vehicle Information 2000 Ford Excursion Limited 7.3L
Issue + Repair History
- Initially brought in for smog certification, failed due to incomplete monitors.
- Replaced both batteries.
- Codes P0603, P0672, P0676, P0678, and P0683 stored in memory.
- Glow plugs replaced with Motorcraft plugs from Autozone.
- Valve cover gasket with harness replaced with Dorman 615-201 kit.
- Codes P0676, P0678, and P0683 returned after repairs.
Other OBD2 Codes + Test Results
- P0683: Glow plug controller to PCM communication circuit
- P0676: Glow plug #6
- P0678: Glow plug #8
- Ohm tested com circuit pink/orange wire – OK, no resistance
Mechanic Suggestions
- Check for any bent or recessed pins on the circuit board.
- Secure the connector with zip ties or twisted wires for testing purposes.
- Verify the wire integrity by back-probing from the origin at the PCM harness connector.
- Inspect the engine wiring harness for any faults.
- Consider replacing the harness side glow plug harness with OEM parts.
Final Fix
- Determined that a remanufactured Cardone module was faulty.
- Replaced the module with a new one from WorldPac.
- Found a square wave signal on the output signal.
- Passed glow plug test with scantool, road tested to complete monitors, and passed emissions inspection.
Case #2: GMC
Vehicle Information 2006 GMC Sierra 2500 HD SLE 6.6L
Issue + Repair History
- Service lamp came on, scanned next day.
- All glow plugs found to have failed.
- Campaign bulletin # 06522 (glow plug module reprogram) already performed.
Other OBD2 Codes + Test Results
- P0671: Glow plug #1
- P0672: Glow plug #2
- P0673: Glow plug #3
- P0674: Glow plug #4
- P0675: Glow plug #5
- P0676: Glow plug #6
- Tested all 8 glow plugs – all failed
Mechanic Suggestions
- Replace all glow plugs as it’s a common issue.
- If old controller is present, replace it and ensure proper programming with Tech 2.
- Verify glow plug resistance and check for blown fuses.
- Remove add-on remote starter or alarm kits before replacing glow plugs.
- Glow plugs may slowly lose resistance over time, leading to eventual failure.
Final Fix
- Replaced all glow plugs despite initial doubts about simultaneous failure.
- Found no glow plug relay; vehicle uses GPCM for powering the plugs.
- Decided against replacing GPCM as it was working correctly.
- Glow plugs replaced; vehicle returned to normal operation.
Case #3: Chevrolet
Vehicle Information 2007 Chevrolet Express 2500 6.6L
Issue + Repair History
- Complaints of power loss.
- Scan data shows balance rates are good, but code indicates leaky cylinder 8 injector.
- Planning to replace 4 injectors on the left side and some glow plugs.
Other OBD2 Codes + Test Results
- P02b9: Cylinder 8 injector leaking
- P0672: Glow plug cylinder 2
- P0674: Glow plug
- P0676: Glow plug
- P0677: Glow plug
Mechanic Suggestions
- Consider having a diesel technician perform the injector replacement.
- Check for fuel line restrictions if there’s a loss of power.
- Glow plug issues won’t cause loss of power, focus on injector replacement.
- Stall test recommended if the van is used heavily to check for torque converter issues.
- Use a Tech 2 or compatible scanner to program flow rates into PCM and glow plug control module after injector replacement.
Final Fix
- Discovered a broken return line tee on cylinder 8 injector and collapsing fuel lines.
- Replaced leaking injector and addressed fuel line restrictions.
- Glow plugs were found damaged and difficult to remove; postponed replacement until necessary.
- Van runs smoothly after repairs.
How to diagnose P0676
I made you an overview of solving this DTC, based on all the advice that was suggested by certified mechanics to address this issue in previously mentioned service cases.
| Diagnostic Step | Explanation |
|---|---|
| Inspect the glow plug in cylinder 6 | Check the plug for any signs of damage or malfunction; replace if faulty. |
| Check wiring and connectors | Look for any signs of wear, damage, or loose connections that could interrupt the circuit’s function. |
| Test the glow plug control module | Verify that the module is correctly controlling the power to the glow plug and replace if defective. |
| Examine the ECM | Check for any problems that could affect its ability to control the glow plug circuit effectively. |
| Measure glow plug resistance | Ensure that the resistance is within the manufacturer’s specifications to confirm proper operation. |
In these cases, solutions ranged from replacing faulty glow plugs and repairing damaged wiring to replacing control modules that were not functioning correctly. Such actions highlight the importance of thorough diagnostics to accurately pinpoint the root cause of the P0676 code, ensuring the diesel engine’s optimal performance and reliability.
Car Diagnostics Training
- Car Electrical basics
- OBD-II scanner basics
- How to use an OBD reader
- Introduction to a Bi-directional Scan tool
- OBD scanner buyer’s guide + discounts
I test OBD-II scanners and make DIY Engine diagnostics guides to help you solve your car problems without having to depend on the mechanic. A lot of them will try to scam you or are just no help at all. About Juraj Lukacko