P0675 Cylinder 5 Glow Plug Circuit

The P0675 – Cylinder 5 Glow Plug Circuit diagnostic trouble code (DTC) indicates that the engine control system has detected an electrical problem in the glow plug circuit for cylinder 5.

This code is mainly found on diesel engines with five or more cylinders. Unlike a general glow plug system code, P0675 identifies a problem specifically associated with the cylinder 5 glow plug circuit.

The fault can be caused by a defective glow plug, damaged wiring, a poor electrical connection, a blown fuse, or a problem with the glow plug relay or control module.

What Does P0675 Mean?

In simple terms:

The engine control module has detected abnormal electrical operation in the glow plug circuit for cylinder 5.

A simplified circuit is:

Battery → Fuse → Glow Plug Control Module/Relay → Cylinder 5 Glow Plug

The ECM or PCM monitors the glow plug circuit and expects to see a specific electrical response when the glow plug is activated.

If the expected voltage, resistance, or current is not detected, P0675 may be stored.

The problem may involve:

• Open circuit

• Short circuit

• Excessive resistance

• Incorrect current draw

• Poor electrical connection

• Failed glow plug

What Is a Glow Plug?

A glow plug is an electrically heated component used in diesel engines to help the engine start when it is cold.

It does not produce a spark like a gasoline spark plug. Instead, its heating element becomes extremely hot and helps raise the temperature inside the combustion chamber.

This additional heat helps diesel fuel ignite more reliably during cold starting.

On some modern diesel engines, glow plugs continue operating briefly after startup to improve combustion and reduce emissions.

What Does the Cylinder 5 Glow Plug Do?

The cylinder 5 glow plug provides additional heat inside cylinder 5.

When the engine is cold, the glow plug control system activates it for a calculated period.

If the circuit is defective, cylinder 5 may not receive sufficient preheating.

The engine may still start normally in warm conditions, which is why this type of fault can sometimes go unnoticed until colder weather arrives.

What Causes P0675?

Possible causes include:

• Failed cylinder 5 glow plug

• Open glow plug circuit

• Shorted circuit

• Damaged wiring

• Corroded connector

• Loose terminal

• Excessive circuit resistance

• Faulty glow plug relay

• Faulty glow plug control module

• Blown fuse

• Poor power connection

• Poor ground connection

• Damaged glow plug terminal

The actual cause should be confirmed with electrical testing.

Can a Bad Glow Plug Cause P0675?

Yes.

A failed cylinder 5 glow plug is one of the most likely causes.

The heating element can fail internally because of:

• Open circuit

• Excessive resistance

• Internal damage

• Age

• Excessive heat

However, the glow plug should be tested before replacement because the problem could be somewhere else in the circuit.

Can Broken Wiring Cause P0675?

Yes.

A broken wire between the glow plug controller and cylinder 5 can interrupt current flow.

Inspect the wiring for:

• Broken conductors

• Chafing

• Melted insulation

• Corrosion

• Pinched sections

• Poor previous repairs

The engine compartment exposes glow plug wiring to high temperatures and vibration.

Can a Bad Connector Cause P0675?

Yes.

A loose or corroded connector can create excessive resistance or completely interrupt the circuit.

Inspect the cylinder 5 connector for:

• Corrosion

• Loose terminals

• Burn marks

• Bent contacts

• Water contamination

• Poor terminal tension

Can a Blown Fuse Cause P0675?

Yes, depending on the vehicle.

Some diesel engines use dedicated fuses or high-current protection for the glow plug system.

If the fuse is blown, determine why it failed before replacing it.

Can a Bad Glow Plug Relay Cause P0675?

Yes, on vehicles equipped with a conventional glow plug relay.

Older systems may use a relay to control several glow plugs.

Modern systems may instead use an electronic Glow Plug Control Module (GPCM) capable of monitoring and controlling individual glow plug circuits.

Can a Bad Glow Plug Control Module Cause P0675?

Yes.

A defective GPCM may fail to supply the correct electrical current to cylinder 5.

However, if P0675 is the only glow plug code stored, the cylinder 5 glow plug, connector, and wiring should generally be checked first.

Can Low Battery Voltage Cause P0675?

Yes, potentially.

Glow plugs require considerable electrical current.

A weak battery or excessive voltage drop during starting can interfere with glow plug operation.

Check:

• Battery condition

• Battery voltage

• Cranking voltage

• Charging voltage

Can a Bad Alternator Cause P0675?

Potentially, but it is less likely when only cylinder 5 is affected.

A charging-system problem can cause abnormal voltage throughout the vehicle.

If several glow plug codes and voltage-related DTCs are present, inspect the charging system.

Symptoms of P0675

Possible symptoms include:

• Check Engine Light

• Glow plug warning light

• Difficult cold starting

• Extended cranking

• Rough idle after startup

• Engine vibration

• White smoke during cold starts

• Increased emissions

• Poor cold-start performance

When the engine reaches operating temperature, the symptoms may become much less noticeable.

Can P0675 Cause a No-Start Condition?

Usually not by itself.

One failed glow plug normally does not prevent a modern diesel engine from starting in moderate temperatures.

However, starting can become significantly more difficult when:

• Ambient temperature is very low

• Several glow plugs have failed

• Battery voltage is low

• Engine compression is poor

• There are additional fuel-system problems

Can P0675 Cause Hard Starting?

Yes, particularly in cold weather.

Without sufficient preheating in cylinder 5, combustion may be less efficient during the first few engine cycles.

This can result in:

• Longer cranking

• Rough startup

• Uneven combustion

• Temporary engine vibration

Can P0675 Cause White Smoke?

Yes.

If the combustion chamber remains too cold, diesel fuel may not burn completely during startup.

Unburned fuel can produce white or light-colored smoke from the exhaust.

Can P0675 Cause Rough Idle?

Yes, especially during cold operation.

If cylinder 5 does not receive adequate glow plug assistance, it may contribute less effectively to combustion immediately after startup.

This can produce:

• Rough idle

• Engine vibration

• Uneven combustion

• Temporary misfire-like symptoms

Can P0675 Affect Fuel Economy?

Potentially.

One failed glow plug usually has little effect once the engine is fully warm.

However, repeated difficult starting and incomplete cold combustion can increase fuel consumption and emissions.

Is P0675 Related to the Fuel Injector?

Not directly.

P0675 identifies a problem with the cylinder 5 glow plug circuit.

A defective injector can cause similar symptoms, including rough running or smoke, but it normally generates different diagnostic codes.

If the glow plug circuit tests correctly and the engine continues to run poorly, the injector and other engine systems should be investigated separately.

How Is P0675 Diagnosed?

A systematic approach is recommended.

1. Scan for all DTCs

Check for:

• Other glow plug codes

• Injector codes

• Voltage-related codes

• Communication codes

• Engine performance codes

If multiple glow plug codes are stored, investigate the common power supply or control module.

2. Inspect the cylinder 5 glow plug

Check the glow plug and its electrical connection.

3. Test glow plug resistance

Measure resistance according to the manufacturer's specifications.

Do not use a universal resistance value because glow plug specifications differ between engines.

4. Check the wiring

Inspect the circuit between cylinder 5 and the glow plug controller.

5. Inspect the connector

Look for corrosion, loose terminals, heat damage, and poor terminal tension.

6. Check the fuse

Verify the relevant glow plug fuse or high-current protection device.

7. Check control-module power and ground

Confirm that the glow plug controller receives the required power and has a reliable ground.

8. Check the control signal

Verify that the controller is properly commanding cylinder 5.

9. Test the glow plug control module

If the glow plug and wiring are good, the control module may require further testing.

Can a Multimeter Diagnose P0675?

Yes.

A multimeter can be used to check:

• Glow plug resistance

• Circuit continuity

• Supply voltage

• Voltage drop

• Fuse condition

• Ground quality

However, modern glow plug systems can use PWM or electronically regulated current, so a basic voltage measurement may not provide a complete diagnosis.

Can a Clamp Meter Help?

Yes.

A suitable current clamp can measure the current drawn by the cylinder 5 glow plug.

This can help determine whether the glow plug is actually receiving and drawing the expected current.

Can an Oscilloscope Help?

Yes.

An oscilloscope can be useful for advanced diagnosis of electronically controlled glow plug systems.

It can reveal:

• PWM control signals

• Missing control signals

• Abnormal voltage patterns

• Irregular current behavior

What If P0675 Appears With Other Glow Plug Codes?

This is an important diagnostic clue.

If only P0675 is stored, focus first on:

Cylinder 5 glow plug → Connector → Wiring → Individual control circuit

If several glow plug codes appear simultaneously, investigate:

• Glow plug control module

• Main power supply

• Ground

• Fuse

• Battery voltage

• Glow plug relay

A common electrical fault may be affecting several cylinders.

What If P0675 Appears With P0670?

P0670 generally concerns the glow plug control module/control circuit, while P0675 identifies the cylinder 5 glow plug circuit.

If both codes are present, check the control module's power, ground, and main wiring before replacing individual glow plugs.

What If P0675 Appears Only in Cold Weather?

This is an important clue.

A weak glow plug or marginal electrical connection may work adequately in mild temperatures but fail to provide sufficient heat during a cold start.

Cold-weather symptoms can include:

• Longer cranking

• Rough startup

• White smoke

• Engine vibration

What If P0675 Appears After Glow Plug Replacement?

Verify:

• Correct glow plug type

• Correct voltage rating

• Proper installation

• Connector seating

• Terminal condition

• Wiring condition

A glow plug that physically fits may still have incorrect electrical characteristics for the engine.

What If P0675 Returns Immediately After Clearing?

If the code returns immediately, the fault is probably still present.

Focus on:

• Open glow plug

• Shorted circuit

• Broken wire

• Poor connector

• Control-module output

If the problem occurs only under certain temperatures, additional cold-start testing may be required.

What If P0675 Appears After Engine Repair?

Inspect the wiring around cylinder 5 carefully.

Engine repairs can result in:

• Disconnected connectors

• Pinched wires

• Damaged harnesses

• Loose grounds

• Incorrectly routed wiring

Is P0675 a Serious Code?

Usually, P0675 is not an immediate engine-damage emergency.

However, it should be repaired because it can cause:

• Difficult cold starts

• Longer cranking

• Increased starter load

• Increased battery load

• Rough cold operation

• Increased emissions

• White smoke

The problem becomes more significant as ambient temperatures decrease.

Can You Drive With P0675?

Usually, yes, if the engine starts and runs normally.

A single glow plug circuit fault generally does not prevent normal driving.

However, the fault should not be ignored for an extended period, especially if:

• Cold starting becomes difficult

• Several glow plug codes are present

• Excessive smoke appears

• The engine runs very roughly after startup

How Is P0675 Repaired?

The repair depends on the confirmed cause.

Possible repairs include:

• Replacing the cylinder 5 glow plug

• Repairing damaged wiring

• Repairing the connector

• Replacing damaged terminals

• Repairing a fuse or power supply

• Replacing the glow plug relay

• Replacing the glow plug control module

• Repairing a poor ground

• Correcting an incorrect glow plug installation

Does P0675 Require Replacing All Glow Plugs?

Not necessarily.

If testing confirms that only cylinder 5 has a failed glow plug, replacing all glow plugs may not be necessary.

However, if the glow plugs are old and several are showing signs of deterioration, replacing them as a set may be considered according to the manufacturer's recommendations.

Should the Glow Plug Be Tested Before Replacement?

Yes.

The complete circuit should be tested before replacing components.

The diagnosis should distinguish between:

Failed cylinder 5 glow plug

and

Fault in the cylinder 5 glow plug circuit

A new glow plug will not repair a broken wire, damaged connector, or faulty control module.

Common Diagnostic Mistakes

Replacing the glow plug without checking the wiring

A broken circuit will remain faulty after installing a new glow plug.

Replacing all glow plugs immediately

P0675 specifically identifies cylinder 5.

Using the wrong glow plug

The replacement must match the engine's electrical and physical specifications.

Ignoring the connector

A loose or corroded terminal can create excessive resistance.

Relying only on resistance

Some modern glow plug systems require current or waveform testing for a complete diagnosis.

P0675 vs. Other Cylinder Glow Plug Codes

The primary difference is the cylinder identified by the code.

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

P0677 → Cylinder 7 Glow Plug Circuit

P0678 → Cylinder 8 Glow Plug Circuit

P0679 → Cylinder 9 Glow Plug Circuit

P0680 → Cylinder 10 Glow Plug Circuit

P0681 → Cylinder 11 Glow Plug Circuit

P0682 → Cylinder 12 Glow Plug Circuit

The diagnostic principle is essentially the same for each cylinder-specific glow plug code.

How Do You Clear P0675?

The correct procedure is:

Scan the vehicle → Record all DTCs → Inspect cylinder 5 glow plug → Test resistance/current → Inspect connector → Check wiring → Check fuse → Verify control-module power and ground → Test control output → Repair the confirmed fault → Clear DTCs → Perform a cold-start test → Rescan

If P0675 returns, the cylinder 5 glow plug circuit still has an unresolved problem.

Final Thoughts on P0675

P0675 – Cylinder 5 Glow Plug Circuit indicates an electrical problem involving the glow plug circuit for cylinder 5.

Possible causes include a failed glow plug, damaged wiring, loose or corroded connector, excessive circuit resistance, faulty glow plug relay or control module, blown fuse, or poor electrical connection.

The important point is that P0675 does not automatically mean the glow plug itself has failed. The complete circuit should be tested before replacing components.

The most effective diagnostic sequence is:

Test the cylinder 5 glow plug → Inspect the connector → Check wiring → Check fuse and power supply → Verify ground → Test the control signal → Evaluate the glow plug control module.

If the vehicle has hard cold starting, white smoke, rough idle, or increased cranking time, the glow plug circuit should be repaired before colder weather makes the symptoms more severe.