P0675 – Cylinder 5 Glow Plug Circuit

System: Powertrain | Standard: ISO/SAE Controlled | Fault type: Circuit | Location: Cylinder 5

Definition source: SAE J2012/J2012DA (industry standard)

P0675 is a powertrain diagnostic trouble code that indicates a detected problem in the Cylinder 5 Glow Plug Circuit. Glow plugs are part of the cold-start heating system on certain engines, and the control module monitors the electrical behavior of each cylinder’s glow plug circuit to confirm it can be commanded on and off as intended. When the module sees an electrical condition in the cylinder 5 circuit that falls outside what it expects, it can set P0675 and may illuminate the malfunction indicator lamp. Diagnostic behavior, monitor strategy, and pinpoint test steps vary by vehicle, so confirm circuit routing, connector locations, and test specifications using the appropriate service information before replacing any parts.

What Does P0675 Mean?

P0675 means the control module has identified a fault in the Cylinder 5 Glow Plug Circuit. Based on the official definition, the issue is specific to the electrical circuit associated with the glow plug for cylinder 5, not a general engine performance code. The module’s diagnostics focus on whether the commanded glow plug operation produces the expected electrical response in that circuit. Because this is a circuit-type fault, diagnosis should prioritize verifying the integrity of the wiring, connectors, power supply, and ground paths associated with the cylinder 5 glow plug circuit, then confirming the glow plug and any related control hardware operate correctly.

Quick Reference

  • Subsystem: Cylinder 5 glow plug electrical circuit (command/control and feedback path, varies by vehicle).
  • Common triggers: Open circuit, short to ground or power, excessive resistance, poor connector contact, or an electrical failure of the glow plug or its control path.
  • Likely root-cause buckets: Wiring/connector issues; glow plug (actuator) fault; power/ground distribution; glow plug control device (module/relay, varies by vehicle); control module driver circuit (less common).
  • Severity: Usually moderate; may cause hard starting and rough running during cold starts, typically less noticeable once warmed.
  • First checks: Confirm cylinder numbering, inspect connector/pigtail at cylinder 5, check related fuses/feeds, scan for companion glow plug circuit codes, and review freeze-frame data.
  • Common mistakes: Replacing the glow plug without testing the circuit, misidentifying cylinder 5, ignoring power/ground issues, or overlooking connector pin-fit/corrosion.

Theory of Operation

The glow plug system preheats the combustion chamber area to improve ignition quality during cold starts. A control module (which may be integrated into another module or be a dedicated controller, depending on vehicle design) commands current to each glow plug either individually or through grouped outputs. The cylinder 5 glow plug is supplied through a dedicated wire path and connector, and the system relies on solid power and ground paths to deliver the required heating energy.

To determine whether the circuit is operating correctly, the module monitors the electrical response of the cylinder 5 circuit during commanded operation. This monitoring may be based on measured current flow, voltage behavior at the driver, or internal diagnostics that detect opens/shorts and abnormal electrical characteristics. If the observed circuit behavior does not match expected behavior during a self-test or an active glow event, the module can set P0675.

Symptoms

  • Hard start: Extended cranking or reluctance to start, especially in cold ambient temperatures.
  • Rough idle: Uneven idle immediately after start that improves as the engine warms.
  • White smoke: Increased white exhaust smoke briefly after a cold start due to incomplete combustion.
  • MIL on: Malfunction indicator lamp illuminated with P0675 stored.
  • Cold misfire: Misfire-like shake during the first moments of operation, often temperature-dependent.
  • Reduced cold drivability: Hesitation or poor response right after startup that diminishes with heat.

Common Causes

  • Open circuit or high resistance in the cylinder 5 glow plug feed wire between the control module and the glow plug
  • Poor connection at the cylinder 5 glow plug connector (loose fit, corrosion, terminal push-out, damaged locking)
  • Open or shorted cylinder 5 glow plug (internal element failure that changes circuit load)
  • Short to ground on the cylinder 5 glow plug control circuit causing abnormal current flow during commanded operation
  • Short to power on the cylinder 5 glow plug control circuit causing unintended energizing or incorrect feedback
  • Shared power supply issue affecting glow plug operation (fuse, relay, supply splice, or distribution fault; varies by vehicle)
  • Ground path problem for the glow plug system (engine ground strap, ground junction, or ground eyelet; varies by vehicle)
  • Glow plug control module/driver fault for cylinder 5 output (if individually controlled; varies by vehicle)
  • Harness damage near heat/vibration points causing intermittent opens/shorts in the cylinder 5 circuit

Diagnosis Steps

Tools typically needed include a scan tool with freeze-frame and data logging, a digital multimeter, and back-probing or breakout leads. A test light or fused jumper may help for basic load checks where appropriate. If available, use the service information wiring diagram and connector views to identify the correct cylinder 5 circuit, module pin, and any inline connectors.

  1. Confirm the DTC is P0675 and record freeze-frame data and any related codes (especially other glow plug circuit codes). Clear codes and see if P0675 resets immediately or only after a cold start command.
  2. Verify cylinder numbering for cylinder 5 using service information (varies by vehicle). Misidentifying the cylinder is a common cause of wasted testing.
  3. Perform a visual inspection of the cylinder 5 glow plug area: look for melted insulation, chafing, oil saturation at the connector, broken retainers, or contact with hot/sharp surfaces. Repair obvious harness damage before deeper testing.
  4. Key off, disconnect the cylinder 5 glow plug connector and inspect terminals on both sides for corrosion, spread pins, terminal push-out, and poor pin fit. Correct terminal issues and ensure connectors fully latch.
  5. Test the cylinder 5 glow plug itself per service information using an ohmmeter check and/or a controlled load check method recommended for the platform. Compare results with a known-good cylinder glow plug only as a reference, not as a universal specification.
  6. Check for an open or short in the cylinder 5 control wire between the glow plug and the control module/driver: verify continuity end-to-end and verify there is no continuity to ground or to battery positive when it should be isolated (consult wiring diagrams; varies by vehicle).
  7. With the circuit connected, perform voltage-drop testing on the power/feed path and the ground/return path while the glow plug is commanded on (using a scan tool output test if supported). Excessive drop indicates high resistance in wiring, connectors, splices, relay contacts, or grounds.
  8. Use live data (or bidirectional control) to command glow plug operation and monitor any available glow plug feedback/diagnostic PIDs. Log data while repeating the command to capture intermittent behavior and to correlate the fault with command state.
  9. Perform a wiggle test: while commanding the system or during a cold-start enable window, gently move the harness and connectors for cylinder 5 and related shared loom sections. If the fault toggles, isolate the exact segment and repair the wiring/terminal condition.
  10. Verify shared supply integrity if the design uses a common feed: check relevant fuses/relays and distribution points under the same operating conditions that set the code (often cold start). A supply problem can present as a single-cylinder circuit code depending on driver feedback design.
  11. If wiring, connectors, power/ground paths, and the glow plug test good, follow service information to test the driver stage/control module for the cylinder 5 output (if individually controlled). Confirm pin fit and connector condition at the module before condemning electronics.

Professional tip: Many glow plug circuit faults only appear during a narrow operating window when the module actually commands pre-heat or after-glow. Use scan tool logging and repeatable conditions (cold soak when applicable) so you can test the circuit under load; static continuity checks alone can miss high-resistance terminals and heat-related intermittent opens.

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Factory repair manual access for P0675

Check repair manual access

Possible Fixes & Repair Costs

Repair costs for P0675 vary widely because the fix depends on what testing confirms in the cylinder 5 glow plug circuit, the component locations, and labor access. Always diagnose the circuit first so you replace or repair only the proven fault.

  • Repair or replace damaged wiring in the cylinder 5 glow plug circuit (chafed insulation, broken conductor, melted section)
  • Clean, tighten, or replace corroded/loose connectors and terminals (glow plug, harness connectors, or control-side connections)
  • Replace the cylinder 5 glow plug if it fails electrical testing (for example, out-of-spec resistance or internal open/short verified by procedure)
  • Repair the power feed or ground path affecting the cylinder 5 glow plug circuit (including high-resistance connections found by voltage-drop testing)
  • Repair pin-fit issues (spread terminals) and restore proper terminal tension where intermittent contact is confirmed
  • Replace the glow plug control component only after confirming correct power/ground and that the circuit and glow plug test good

Can I Still Drive With P0675?

In many cases the vehicle may still be driveable, but P0675 can lead to hard starting, extended cranking, rough running for a short time after start, and increased exhaust smoke—especially when the engine is cold. If you experience a no-start condition, severe misfire/roughness, reduced power that affects safe acceleration, or any warning indicating impaired braking or steering, do not drive; diagnose and repair first. Otherwise, minimize cold starts and schedule service soon to prevent repeated start stress and worsening symptoms.

What Happens If You Ignore P0675?

Ignoring P0675 can result in progressively harder cold starts, longer crank times, rough idle after start, and increased emissions and smoke during warm-up. Repeated extended cranking can add wear to the starting system and increase battery stress. If the underlying issue is wiring-related, continued vibration and heat cycling can turn an intermittent circuit problem into a consistent failure.

Compare nearby cylinder glow trouble codes with similar definitions, fault patterns, and diagnostic paths.

  • P0682 – Cylinder 12 Glow Plug Circuit
  • P0681 – Cylinder 11 Glow Plug Circuit
  • P0680 – Cylinder 10 Glow Plug Circuit
  • P0679 – Cylinder 9 Glow Plug Circuit
  • P0678 – Cylinder 8 Glow Plug Circuit
  • P0677 – Cylinder 7 Glow Plug Circuit

Key Takeaways

  • P0675 indicates a fault detected in the cylinder 5 glow plug circuit, not a guaranteed failed glow plug.
  • Wiring, connector condition, and power/ground integrity are common root-cause areas and should be tested first.
  • Use test-driven diagnostics (including voltage-drop checks and wiggle testing) to confirm the exact failure point.
  • Cold-start complaints are the most common impact; severity varies by vehicle and ambient temperature.
  • Replacing modules or multiple glow plugs without circuit verification is a common and costly mistake.

Vehicles Commonly Affected by P0675

  • Diesel-equipped vehicles that use individual glow plugs per cylinder
  • Light-duty trucks and utility vehicles with glow plug preheating systems
  • Passenger vehicles with electronically controlled glow plug circuits
  • Vehicles operated in cold climates or with frequent short trips (more glow plug cycling)
  • Higher-mileage vehicles with aged engine-bay wiring and connectors
  • Vehicles with recent engine work where connectors may be disturbed or harnesses rerouted
  • Vehicles exposed to moisture, road salt, or under-hood contamination affecting terminals
  • Vehicles with aftermarket electrical additions that may alter routing or grounds (varies by vehicle)

FAQ

Does P0675 mean the cylinder 5 glow plug is bad?

No. P0675 means a fault was detected in the cylinder 5 glow plug circuit. The glow plug itself may be faulty, but the same code can be caused by wiring damage, poor terminal contact, power/ground issues, or a control-side problem. Testing is required to identify the failed part of the circuit.

Will P0675 always cause a check engine light and noticeable symptoms?

Not always. Some vehicles may set the code with minimal noticeable symptoms, especially in warm conditions. In colder conditions, symptoms like extended cranking, rough idle after start, or increased smoke during warm-up are more likely. Indicator behavior and symptom severity vary by vehicle and calibration.

Can a wiring issue set P0675 intermittently?

Yes. A loose connector, poor pin fit, corrosion, or a harness section that intermittently opens due to vibration or heat can cause sporadic faults. A wiggle test during circuit checks and reviewing scan tool data over time can help confirm an intermittent circuit problem.

If I replace the glow plug, do I need to do anything else?

After replacing any component, confirm the circuit is healthy by checking connector condition, verifying power/ground integrity, and ensuring there is no harness damage near hot or moving parts. Then clear the code and verify the monitor completes and the fault does not return. Exact verification steps vary by vehicle, so follow service information.

Can P0675 be caused by a control module?

It can, but control-side failure should be considered only after confirming the cylinder 5 glow plug tests correctly and the wiring, connectors, power feed, and grounds are all good. Many repeat comebacks occur when a control component is replaced before finding a high-resistance connection or an intermittent open in the harness.

Always confirm cylinder numbering and the physical location of cylinder 5 using service information before testing or replacing any parts.