Glow plug circuit issues in cylinder 7 of diesel engines, highlighted by diagnostic code P0677, often stem from faults in the electrical components crucial for cold-start efficiency. Problems may include a faulty glow plug, corroded wiring impairing electrical flow, or malfunctioning components in the glow plug control module. Symptoms such as starting difficulties, rough idling, and increased emissions are common, impacting vehicle performance and emissions quality. Diagnostics require tools like a multimeter and OBD-II scanner to assess circuit health and pinpoint faults accurately. Addressing these issues promptly enhances engine reliability and prevents further damage, revealing insights into optimal vehicle maintenance strategies.
P0679 VW Code Meaning
The P0679 code in Volkswagen cars points to a glow plug problem in cylinder 9, usually in diesel engines.
Glow plugs help start the engine in cold weather by heating the combustion chamber. If this code appears, it might mean the glow plug isn't working right, there's an issue with the wiring, or the control module is faulty.
A glow plug with the wrong resistance can mess up the electrical flow, making the engine run poorly. Bad wiring or loose connections can break the circuit, leading to more pollution and damage.
To fix this code, mechanics first check if the glow plug's resistance matches Volkswagen's standards. If the glow plug is bad, it needs replacing.
They also look at the wiring and control module for problems. Not fixing these could harm the engine and exhaust, leading to expensive repairs.
Error Code P0679 Symptoms
Volkswagen's P0679 error code points to a problem with the glow plug in cylinder 9. This can cause several issues with the car, especially when it's cold outside.
- Hard to Start: The engine may have trouble starting because the glow plug isn't heating the chamber enough, making it harder to ignite the fuel-air mix.
- Rough Running: The car might idle roughly or misfire now and then. This happens because the glow plug isn't working right, so the engine doesn't burn fuel smoothly.
- Wastes More Fuel: If the glow plug isn't doing its job, the engine might use more fuel. This is because the fuel isn't burning completely.
- More Pollution: The car may produce more emissions. When the fuel doesn't burn well, it leads to more exhaust, which can affect how clean the car runs.
In some cases, the car might even stall, so fixing this issue is necessary to keep the vehicle running well.
Causes of VW P0679 Fault Code
The P0679 code shows a problem with the glow plug in cylinder 9 of a Volkswagen diesel engine. Here are some common reasons this might happen:
- Bad Glow Plug: If the glow plug in cylinder 9 isn't working, it won't heat properly. This can mess up how the engine burns fuel. Check and change glow plugs regularly to keep things running smoothly.
- Wiring Problems: If the wires leading to the glow plug are rusty or broken, the electricity won't flow right. This can happen because of weather or just wear and tear. Look closely at the wires and connections.
- Glow Plug Control Module Issues: This part helps glow plugs work correctly. If it's broken, the glow plugs might not work well or at all. Check if this module needs fixing or replacing.
- Engine Control Module (ECM) Issues: The ECM helps manage the glow plugs. If there's a problem here, it can cause the P0679 code to pop up. You might need to update the software or replace this module.
Tools Needed to Diagnose
To figure out what's wrong with the P0679 fault code, you'll need some specific tools to check and fix the glow plug circuit.
Here are the tools you'll need to use:
- Multimeter: This device checks voltage and resistance. It helps find broken parts in the glow plug circuit by checking if electricity flows correctly.
- OBD-II Scanner: This tool reads error codes related to the glow plug circuit. It helps pinpoint problems with cylinder 7.
- Wire Strippers and Crimpers: Use these tools to check and fix any broken wires or connections. Keeping the wiring in good shape is important for the glow plug to work well.
- Test Light: This tool checks if there's power reaching the glow plug connector. It's a basic step to make sure the circuit is working before you change any parts.
How to Fix P0679 VW Error Code – Step by Step
Step 1:
Begin by using a multimeter to assess the glow plug in cylinder 7. Perform continuity and resistance checks. The resistance should typically range between 0.5 to 2 ohms. If values fall outside this range, the glow plug is defective and needs replacement.
Step 2:
Examine the wiring and connections relevant to the glow plug circuit. Inspect for visible signs of damage or corrosion, which can impede electrical flow. Repair or replace any damaged wires to restore proper function.
Step 3:
If the glow plug and wiring are intact, proceed to test the glow plug control module. This module is crucial for timing and voltage regulation, and a malfunction can trigger the error code. Replace the module if testing reveals faults to ensure optimal performance.
Step 4:
Once repairs are complete, utilize an OBD-II scanner to erase the diagnostic trouble code from the engine control module. This step ensures no residual data interferes with engine performance.
Step 5:
Conduct a test drive to confirm that the engine initiates and operates without issues linked to the glow plug circuit. This guarantees comprehensive problem resolution.
Common Diagnosis Mistakes
When fixing the P0679 VW error code for cylinder 7, be aware of common mistakes that can make repairs ineffective. Errors in diagnosing can lead to unnecessary part changes and miss the real problem. Technicians should use a wide-ranging approach to diagnose the issue fully.
- Glow Plug Assumptions: Many think the error code always means the glow plug is faulty. This can distract from checking the wiring or circuit, which might also be causing the issue.
- Ignoring the Control Module: Sometimes, people don't inspect the glow plug control module. If this part is faulty, it can affect several glow plugs. Missing this can lead to wrong fixes.
- Skipping Wiring Checks: Not checking the wiring harness for rust or damage can mean missing problems that affect how the glow plug circuit works. Thorough checks can find hidden issues.
- Resistance Testing Errors: Mechanics might not test the glow plug's resistance correctly. This can lead to wrong conclusions about whether the glow plug needs replacing. Proper testing is key to deciding on a replacement.
P0679 VW Repair Cost
Fixing the P0679 code in a Volkswagen can cost between $100 and $300. This range covers simple fixes like replacing a glow plug or fixing wiring problems in the glow plug circuit.
If the issue involves the glow plug control module, costs might rise to $200-$500. The total cost depends on the problem's complexity and how long it takes to figure out what's wrong. Local labor rates also play a part. Getting a detailed quote from a trusted mechanic is wise.
The cost can vary depending on the Volkswagen's make and model. High-performance models might have more expensive parts and labor compared to standard models.
Think about both the repair costs now and potential savings from better vehicle performance later. Sometimes, replacing the glow plug control module may improve reliability, especially if you drive a lot in cold weather.
A skilled mechanic can help ensure repairs match your vehicle's needs and your expectations.
Related Error Codes on Volkswagen
Volkswagen cars sometimes have problems with glow plugs, which can affect how well the engine runs. Specific error codes like P0678 and P0677 show issues with the glow plug circuits in cylinders 8 and 7. These problems can lead to more pollution and use more fuel. Other codes from P0671 to P0678 also point to troubles with glow plugs or their circuits, hinting at bigger system issues.
For a wider check, the P0670 code warns of general problems in the glow plug circuits. This could impact several cylinders, including number 7. Such issues might come from the control module or wiring. Ignoring these alerts can cause higher emissions, lower fuel efficiency, and possible engine problems.
| Error Code | Cylinder | Problem |
|---|---|---|
| P0671 | 1 | Glow plug issue |
| P0677 | 7 | Glow plug issue |
| P0678 | 8 | Glow plug issue |
| P0670 | Multiple | General glow plug problem |
| P0678 | 8 | Circuit or plug issue |
Fixing these codes helps the car run smoothly and avoids engine troubles.
Can I drive safely with P0679 VW?
No, you shouldn't drive safely with a P0679 VW error.
This code means there's a problem with the glow plug in cylinder 9, which can make the engine start poorly and run rough.
It might stall, making driving unsafe.
Get it fixed soon!
People Also Ask
What Is the Function of a Glow Plug in a Diesel Engine?
Glow plugs help diesel engines start in the cold. They heat up the engine's air and fuel mix so it can ignite easily. This makes the engine work better and reduces pollution, especially when it's really cold outside.
How Does a Glow Plug Circuit Operate in a Vehicle?
A glow plug circuit helps start a diesel engine by sending electricity to glow plugs. These plugs quickly heat up to make the air and fuel mixture ignite easily, especially when it's cold. A control module makes sure the process happens smoothly.
What Are the Signs of a Failing Glow Plug Circuit?
When a glow plug circuit is failing, the car might be hard to start, especially when it's cold. The engine can run rough or misfire, use more fuel, and give off smoky exhaust. Sometimes, the engine might even stop running because it doesn't burn fuel well.
Can a Faulty Glow Plug Affect Fuel Efficiency?
Yes, a bad glow plug can make your car use more fuel. It can cause the engine to burn fuel poorly, which means your car might run rough and use more gas. Fixing glow plug problems helps your car run better and save fuel.
How Often Should Glow Plugs Be Replaced in a Vehicle?
Glow plugs usually need to be changed every 60,000 to 100,000 miles. How often depends on what the car maker says and how you drive. Checking them regularly can help find problems early, keeping your car running well and making the glow plugs last longer.