P0674 Cylinder 4 Glow Plug Circuit Malfunction

P0674 – OBD-II Trouble Code Technical Description

Trouble code P0674 is a general trouble code that indicates a fault in the cylinder 4 glow plug circuit. 

What does the fault code mean P0674?

Trouble code P0674 indicates a problem in the cylinder 4 glow plug circuit. This means that the engine management system has detected an abnormal voltage in this circuit that is not within the manufacturer's specification standards. The result is a malfunction that may affect engine performance.

Possible reasons

Some possible reasons for the P0674 trouble code:

• Defective glow plug: The most common cause is a failure of the glow plug itself in cylinder 4. This may be due to wear, damage or corrosion.
• Wiring or connectors: The wiring or connectors connecting the glow plug to the engine control module may be damaged, broken, or oxidized.
• Engine Control Module (PCM) malfunction: Problems with the engine control module, which controls the glow plugs, can cause trouble code P0674.
• Problems with the electrical system: Problems with the vehicle's electrical system, such as low battery voltage or problems with the alternator, can cause P0674.
• Mechanical problems: For example, compression problems in cylinder 4 can cause the glow plug to malfunction, resulting in a P0674 code.
• Malfunction of other components of the ignition system: For example, problems with the preheat system that controls the glow plugs can cause trouble code P0674.

These reasons are the most common, however the actual cause may be unique to a particular vehicle. For an accurate diagnosis, it is recommended to contact a professional auto mechanic or service center.

What are the symptoms of a fault code? P0674?

Symptoms associated with Trouble Code P0674 (Cylinder 4 Glow Plug Circuit Problem) can vary and may vary depending on the specific situation and engine type, some common symptoms that may occur are:

• Difficulty starting the engine: Problems with one of the glow plugs can make the engine difficult to start, especially in cold weather. This may manifest itself as prolonged cranking of the starter or several unsuccessful starting attempts.
• Poor engine performance: If the glow plug in cylinder 4 is not working properly, it can cause the engine to run rough, lose power, shake, or even misfire.
• Frequent engine stops: If the glow plug is faulty, frequent shutdown of cylinder 4 may occur, which may cause the engine to stop frequently or even shut down while driving.
• Increased emissions of harmful substances: Incorrect glow plug operation can result in imperfect fuel combustion, which can increase emissions and lead to problems with environmental standards.
• Check Engine Light: When P0674 occurs, the Check Engine Light will turn on on your vehicle's dashboard. This signal indicates that there is a problem with the system and requires diagnostics.

How to diagnose a fault code P0674?

To diagnose DTC P0674, follow these steps:

1. Scanning error codes: Use a diagnostic scanner to read error codes from the engine control module. Make sure the P0674 code is present and make a note of it for further diagnosis.
2. Checking the glow plugs: Check the condition of the glow plugs in cylinder 4. Inspect them for wear, damage or corrosion. Replace them if necessary.
3. Checking wiring and connectors: Inspect the wiring connecting the glow plug to the engine control module. Check for damage, breaks or corrosion. Carefully check the condition of connections and connectors.
4. Using a multimeter: Use a multimeter to check the voltage in the cylinder 4 glow plug circuit. Make sure the voltage is within manufacturer specifications.
5. Engine Control Module (PCM) Diagnostics: Check the operation of the engine control module for errors or malfunctions. Reprogram or replace the PCM if necessary.
6. Checking other components: Check other ignition and electrical system components such as battery, alternator, relays and fuses that may affect glow plug performance.
7. Recheck: After performing all required diagnostic procedures, scan the Engine Control Module again to ensure that DTC P0674 no longer appears.

If you are unable to diagnose or resolve the problem yourself, it is recommended that you contact a qualified auto mechanic or service center for further diagnosis and repair.

Diagnostic errors

When diagnosing DTC P0674, the following errors may occur:

• Incorrect interpretation of error code: The error may occur if the P0674 code is not interpreted correctly or if other possible causes are not fully diagnosed.
• Other components are faulty: Focusing only on the cylinder 4 glow plugs may miss another problem that could cause the same error. For example, faulty wiring, connectors or engine control module.
• Incorrect component replacement: If the cylinder 4 glow plugs were replaced without proper diagnosis or if the faulty part was not replaced, the problem may continue.
• Skipping electrical circuit diagnostics: Incorrect diagnosis or failure to test the electrical circuit connecting the glow plug to the engine control module can lead to erroneous conclusions.
• Incorrect Cause Detection: Sometimes the cause of the P0674 code may not be obvious or may require additional tests or tools to identify.
• Problems with the multimeter or other tools: Improper use or calibration of diagnostic tools such as a multimeter can result in incorrect measurements and diagnostics.

To avoid these mistakes, it is important to carry out a thorough and systematic diagnosis, following the manufacturer's manual and using the correct tools and methods.

How serious is the fault code? P0674?

Trouble code P0674 should be considered a serious problem because it indicates a faulty cylinder 4 glow plug circuit. A faulty glow plug can result in difficult starting, rough running, loss of power and increased emissions. Moreover, if a faulty glow plug is not corrected, it can cause serious engine damage, especially under cold starting conditions. Therefore, it is recommended that you contact a qualified auto mechanic immediately for diagnosis and repair to prevent further problems and ensure the safety and reliability of your vehicle.

What repair will help eliminate the code? P0674?

To resolve DTC P0674, remove or replace the following components:

1. Glow plugs: Check the glow plugs in cylinder 4 for wear, damage or corrosion. If necessary, replace them with new ones.
2. Wiring and Connectors: Check the wiring and connectors connecting the glow plug to the engine control module for damage, breaks or corrosion. Repair or replace connections as necessary.
3. Engine Control Module (PCM): Check the operation of the engine control module for errors or malfunctions. If problems are found, reprogram or replace the PCM.
4. Electrical system: Check the condition of the vehicle's electrical system, including the battery, alternator, relays and fuses. Make sure the glow plug circuit voltage is within manufacturer specifications.
5. Mechanical problems: Check cylinder 4 compression and other mechanical aspects of the engine. Repair or maintenance may be required if problems are found with mechanical components.

After thoroughly diagnosing and determining the cause of the malfunction, carry out the necessary repair work. If you are unsure of your skills or experience, it is best to contact a qualified auto mechanic or service center for diagnosis and repair.

How to Fix P0674 Engine Code in 3 Minutes [2 DIY Methods / Only $9.74]

P0674 – Brand-specific information

Trouble code P0674 refers to problems with the cylinder 4 glow plug circuit, and is specific to some vehicle brands:

• Ford, Lincoln, Mercury: Cylinder 4 Glow Plug Circuit/Open – Cylinder 4 glow plug system open or open circuit.
• Chevrolet, GMC, Cadillac: Cylinder 4 Glow Plug Circuit/Open – Cylinder 4 glow plug circuit malfunction.
• Dodge, Chrysler, Jeep: Cylinder 4 Glow Plug Circuit/Open – Cylinder 4 glow plug system open or open circuit.
• Volkswagen, Audi, Seat, Skoda: Cylinder 4 Glow Plug Circuit/Open – Cylinder 4 glow plug circuit malfunction.
• BMW, Mini: Cylinder 4 Glow Plug Circuit/Open – Cylinder 4 glow plug circuit malfunction.
• Toyota, Lexus: Cylinder 4 Glow Plug Circuit/Open – Cylinder 4 glow plug circuit malfunction.
• Mercedes-Benz: Cylinder 4 Glow Plug Circuit/Open – Cylinder 4 glow plug system open or open circuit.
• Nissan, Infiniti: Cylinder 4 Glow Plug Circuit/Open – Cylinder 4 glow plug circuit malfunction.

Clarification on a specific make and model of car may be required for more accurate diagnosis and repair.