The OBD2 code P0675 indicates a fault in the glow plug circuit of cylinder number 5. Glow plugs are essential for the cold starting of diesel engines, heating the air in the combustion chamber to ensure the engine starts smoothly in cold conditions.
While a glow plug issue might not directly cause stalling in warm conditions, it can indicate underlying electrical or fuel system problems that could lead to engine performance issues, including stalling and difficulties in starting.
P0675 quick overview
| Meaning | P0675: Glow Plug Circuit Malfunction, Cylinder 5 |
| Is it serious? | Yes, especially in cold weather, as it can lead to starting difficulties and potential damage to the engine if misfires occur. |
| Possible causes | – Faulty glow plug in cylinder 5 – Wiring or connection issues in the glow plug circuit – Problems with the glow plug control module – Underlying issues affecting engine performance, unrelated directly to the glow plug system |
| How to diagnose? | Inspect the glow plug in cylinder 5 for damage or wear. Check electrical connections and wiring for corrosion, breaks, or shorts. Test the glow plug control module for proper operation. Monitor system voltage and fuel pressures using a scan tool. Investigate related systems for any signs of coolant leaks or fuel delivery issues that could cause stalling. |
P0675 Meaning
Imagine your diesel engine needs a little help waking up on a cold morning. The glow plugs are like the coffee that warms up the engine’s combustion chambers, making it easier to start. When you get a P0675 code, it’s like finding out your coffee maker isn’t working for one specific cup.
While you might not need that “coffee” to start the engine in warmer weather, the issue could point to bigger problems, like electrical issues or even a coolant leak, that might make the engine “feel sick” and stall. Fixing it involves checking the glow plug itself, the wires that connect to it, and other parts of the engine that might be affected.
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
How to fix P0675 – learn from mechanics
I looked into P0675 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: Chevrolet
Vehicle information 2008 Chevrolet C4500 Kodiak C4C042 6.6L
Issue + repair history
- Engine stalls intermittently, sometimes fails to restart.
- Previously serviced by the dealer multiple times for similar issues, including a recent repair for an exploded intake fuel pump.
- Current symptoms include stalling and low coolant warning.
Other OBD2 Codes + Test Results
- P0675 – Glow plugs: Cylinder Number 5 shows 66.5 ohms and 0 voltage on scan data.
Mechanic suggestions
- Doubts that a glow plug failure could cause stalling, as glow plugs are only used for cold starts.
- Advises checking voltage PIDs and monitoring fuel pressure during the problem occurrence.
- Suggests checking for air leaks in the fuel lines and filter base, as well as inspecting the fuel filter assembly for leaks.
- Recommends a complete module scan to ensure no communication or voltage issues in other modules.
- Proposes using a scan tool to monitor system voltage, fuel pressures, and TAC system operation.
- Mentions a TSB for high-pressure pump regulator issues but expects a related fuel delivery DTC to be stored.
Final fix
- Discovered a coolant leak from the timing cover, triggering the low coolant warning and causing the engine to shut off. Fixing the coolant leak resolved the stalling issue.
Case #2: Chevrolet
Vehicle information 2005 Chevrolet Silverado 2500 HD 6.6L
Issue + repair history
- No start issue with a half-second crank followed by a stall, similar to VTD fuel disable.
- Previous repair attempts include BCM replacement and ignition switch replacement.
- IPC indicator lights are not illuminating during the key-on bulb test.
Other OBD2 Codes + Test Results
- P1626 – Theft deterrent fuel enable signal not received.
- P0675 – Glow plug 5 control circuit.
Mechanic suggestions
- Recommend testing the Passlock sensor and its wiring for any issues.
- Suggest performing a VTD relearn procedure, possibly using the Tech2 for faster execution.
- Advise checking Class 2 Power Mode to ensure it matches the ignition switch position, as the BCM is the Power Mode Master.
- Propose replacing the Passlock sensor, part of the lock cylinder case, if necessary, followed by a VTD relearn.
- Consider checking for fuel system priming issues, such as a lost prime or a faulty filter housing.
- Recommend checking battery cables for corrosion, poor connections, and internal corrosion, as excessive voltage drop during cranking could cause the code.
- Ensure proper programming of the BCM and perform a theft relearn procedure if necessary.
Final fix
- Discovered an open pink wire between the BCM and the underhood fuse box, causing a lack of power on terminal A4 of connector 4 on the BCM. Repairing the open wire resolved the issue, allowing proper communication and resolving the stalling problem.
Case #3: Ford
Vehicle information 2004 Ford F-350 Super Duty Harley-Davidson Edition 6.0L
Issue + repair history
- MIL lamp illuminated.
- Codes for all 8 glow plug circuits present despite the glow plugs being in good condition and the module being new.
- Initial current draw on each glow plug is around 20-22 amps when power is applied, dropping thereafter.
- Glow plug control module has been replaced.
Other OBD2 Codes + Test Results
- P0671 – Cylinder 1 glow plug circuit
- P0672 – Cylinder 2 glow plug circuit
- P0673 – Cylinder 3 glow plug circuit
- P0674 – Cylinder 4 glow plug circuit
- P0675 – Cylinder 5 glow plug circuit
- P0676 – Cylinder 6 glow plug circuit
Mechanic suggestions
- Check the valve cover harness for shorts.
- Inspect the injector harness if the vehicle has glow plugs under valve covers.
- Verify power supply to the glow plug controller.
- Consider a TSB for an updated glow plug module wiring harness connector.
- Examine the wiring feeding B+ to the plugs and control module.
- Investigate ground problems, particularly the ground side of the controller or PCM.
- Check the harnesses at the controller for pins pushing out and the F.I.C.M. for codes/data.
Final fix
- Discovered corrosion in the main power wire connected to the right battery cable. Replaced the cable end and cleaned the battery terminals, resolving the issue.
How to diagnose P0675
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 5 | Check for physical damage or wear that could prevent proper operation. |
| Check wiring and electrical connections | Look for breaks, corrosion, or shorts that could impair the circuit’s integrity. |
| Test the glow plug control module | Ensure it is correctly controlling the power to the glow plugs. |
| Use a scan tool for monitoring | Check system voltage, fuel pressure, and other relevant PIDs that could indicate underlying issues. |
| Investigate coolant leaks and fuel delivery issues | Coolant leaks or fuel system problems could indirectly lead to engine stalling or starting issues. |
The cases presented highlight the complexity of diagnosing and resolving issues related to the P0675 code. From wiring and connection problems to unexpected issues like coolant leaks, each scenario underscores the need for a comprehensive diagnostic approach. This approach should not only focus on the glow plug system but also consider other vehicle systems that could contribute to the symptoms observed, ensuring a thorough resolution to the problem.
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