P0675 — Cylinder 5 Glow Plug Circuit/Open #

Note: The definition of this code may vary depending on the vehicle manufacturer. Always refer to your OEM (Original Equipment Manufacturer) service information for specifics.

• Cylinder 5 Glow Plug Circuit/Open (General, Ford, GM, Chrysler)
• Glow Plug Circuit Open – Cylinder #5 (Volkswagen, Mercedes-Benz)
• Cylindre 5, Circuit Bougie de Préchauffage Ouvert (Renault, Peugeot)

Summary of DTC P0675 #

P0675 is a generic OBD-II trouble code that indicates the Engine Control Module (ECM)—the computer managing engine functions—has detected an electrical fault or open circuit in the glow plug system for cylinder 5. Glow plugs are heating elements used in diesel engines to assist with cold starts by preheating the combustion chambers. When the ECM senses that the circuit for cylinder 5’s glow plug is not functioning as expected, it triggers this code and may illuminate the Check Engine or Glow Plug warning light. This code does not typically affect gasoline engines. Prompt diagnosis is essential, especially in cold climates, as starting and drivability can be affected.

Common Symptoms for DTC P0675 #

A vehicle storing P0675 may present a range of symptoms, from subtle to quite obvious, especially during cold weather. These symptoms are generally related to hard or delayed starting and rough idle, most noticeable when the engine is cold. Here’s what you might notice:

• Hard starting, especially in cold conditions
• Rough idle after startup
• Increased white or gray exhaust smoke during cold starts
• Illuminated Check Engine or Glow Plug warning lamp
• Decreased engine performance immediately after startup
• Possible misfire on cylinder 5 during warm-up

Probable Causes of P0675 (Most to Least Common) #

Glow plug circuit faults can have several root causes. Based on field experience, some issues are more prevalent than others. Here’s an ordered list starting from the most likely:

1. Failed or faulty glow plug on cylinder 5
2. Open circuit or high resistance in the glow plug wiring harness
3. Corroded or loose electrical connectors at the glow plug or harness
4. Faulty glow plug control module (sometimes called a glow plug relay or timer)
5. ECM (Engine Control Module) or PCM (Powertrain Control Module) failure (rare)

Step-by-Step Diagnostic Guide for P0675 #

Tackling a P0675 code systematically can save time and prevent unnecessary parts replacement. Here’s a proven, step-by-step approach:

• Confirm the code with a scan tool and record freeze frame data for context (temperature, RPM, etc.).
• Clear the code and see if it returns after a cold start cycle.
• Visually inspect the glow plug and harness on cylinder 5 for signs of burning, corrosion, or loose connectors.
• Test the resistance of glow plug #5 with a digital multimeter (should typically read less than 2 ohms, but check OEM spec).
• Check for voltage at the glow plug harness connector during pre-glow phase (key ON, engine OFF, cold engine).
• If the plug tests good and wiring is intact, test the output at the glow plug control module for cylinder 5.
• If all components test within specification, consult OEM wiring diagrams and test for continuity from ECM/PCM to glow plug.

Possible Repairs for P0675 #

Once the root cause is identified, repairs should directly address the source of the fault. Here are the most common solutions, matched to their respective causes:

• Replace the faulty glow plug on cylinder 5.
• Repair or replace damaged wiring or connectors in the cylinder 5 glow plug circuit.
• Clean or tighten corroded or loose electrical connections.
• Replace the glow plug control module if it’s not delivering power to the plug.
• Reprogram or replace the ECM/PCM only if all other possibilities are ruled out and manufacturer testing confirms failure.

Is It Safe to Drive with P0675? #

Limited— Driving with a P0675 code is generally possible, especially in mild weather, but it is not recommended for extended periods. In cold climates, you may experience hard starting, excessive smoke, and rough running, which can stress the engine and battery. If ignored, repeated poor cold starts can increase wear on other engine components and potentially cause unburned fuel to contaminate the exhaust system. Address this issue as soon as possible to avoid long-term damage.

Vehicles Most Commonly Affected by P0675 #

While P0675 is a generic code and can appear on any diesel-powered vehicle with OBD-II, it’s most frequently reported on certain makes and models. This reflects both their popularity and known glow plug system issues:

• Ford Super Duty (F-250, F-350, with Power Stroke diesel)
• Chevrolet Silverado/GMC Sierra (Duramax diesel)
• Dodge Ram (Cummins diesel, older models)
• Volkswagen TDI (Jetta, Passat, Golf)
• Mercedes-Benz Sprinter and E-Class diesels
• Renault and Peugeot diesel models (Europe)

Common Mistakes & Best Practices for P0675 #

Technicians and DIYers can save time—and money—by steering clear of these frequent missteps. For best results, keep these tips in mind:

• Don’t replace all glow plugs without proper testing—often only one is faulty.
• Avoid skipping the harness and connector inspection; corrosion and loose contacts are common culprits.
• Don’t overlook the control module or relay—if multiple glow plug codes are set, the module may be at fault.
• Use the correct OEM specification for glow plug resistance and voltage tests.
• Always clear codes and retest after repairs to ensure the problem is resolved.

Quick FAQ for DTC P0675 #

Q: Can I just ignore a P0675 code if my truck starts fine in summer?
A: While warm temperatures may mask starting issues, the code indicates a real fault. Ignoring it can lead to more difficult starts in cold weather and possible engine damage over time.

Q: Is it okay to replace just one glow plug, or should I do them all?
A: If only one glow plug tests faulty, it is usually fine to replace just that one. However, if the plugs are aged or multiple are failing, replacing all at once can prevent future issues.

Q: Will driving with this code damage my engine?
A: Occasional short trips are unlikely to cause damage, but chronic hard starts can lead to unburned fuel, increased engine wear, and potential damage to the diesel particulate filter or catalytic converter.