VW Diesel Engine Malfunction Light (Meaning, Causes + Solution)

VW diesel engine malfunction light

Have you ever wondered what VW diesel engine malfunction means and how to fix that? Well, we got you covered.

When driving a Volkswagen vehicle equipped with a diesel engine, it’s essential to be aware of the various warning lights on the dashboard, especially the diesel engine malfunction light.

This light provides crucial information regarding the performance and health of your vehicle’s engine. In this comprehensive guide, we will discuss the reasons behind the diesel engine malfunction light, what it means, and how to address the issue.

Diesel Engine Pre-Glow Light: The Basics

Due to the nature of diesel engines, they require some extra help when starting at cold temperatures. The glow plug is a heating element that is activated during startup when the engine temperature is too low.

It raises the temperature inside the cylinders to facilitate pressurizing and detonating the diesel fuel. The system typically makes the driver wait around 10 seconds while the plugs warm up the engine.

Once the correct temperature has been achieved, the computer will allow the driver to start the engine.

What the Diesel Engine Pre-Glow Light Means

Normally, the glow plug indicator light will come on only when the engine is cold. In most cases, this light flashes only when an issue has been detected.

The most common reason to replace glow plugs is age. Over time, after repeated warm-up cycles, the glow plugs age and are unable to produce any heat. Replacing any malfunctioning glow plugs should get rid of any issues you are having.

If a new glow plug does not remedy the problem, take a look at other parts of the circuit, mainly the timer. The timer’s job is to turn the plugs off once the correct temperature has been reached. A faulty timer may keep the plugs on for too long, wearing them out, or even not turning the plugs on at all.

If a fault has been detected, the computer will save a code in its memory to help diagnose the issue. A certified technician should hook up a scan tool to your car to read this code.

Is it Safe to Drive with the Diesel Engine Pre-Glow Light On?

Some vehicle engines cannot be started until the glow plug light has turned off, preventing drivers from starting the engine too soon.

You should always wait for the light to shut off before attempting to start the engine. Being patient will help keep your engine going strong in the long run.

Certified technicians are always available if you ever require assistance identifying glow plug issues.

Check Engine Light in Volkswagen Vehicles

In addition to the diesel engine pre-glow light, Volkswagen diesel vehicles are equipped with a check engine light that serves as a general warning indicator for various engine-related issues.

The check engine light is usually a yellow, engine-shaped icon on the dashboard.

Causes and Meaning of the Volkswagen Check Engine Light

While the check engine light may seem intimidating, the reasons behind it can be both minor and major. Some common reasons for the check engine light to come on in a Volkswagen vehicle include:

  • Faulty oxygen sensor
  • Missing or loose gas cap
  • Malfunctioning catalytic converter
  • Faulty airflow sensor
  • Worn spark plugs
  • The thermostat is not working properly

How to Reset the Volkswagen Check Engine Light

The best way to turn off the check engine light is to address the underlying issue causing it. Once the problem has been resolved, you can reset the light using an ODBII diagnostic tool or VCDS.

The light is not designed to be turned off in any other way, although disconnecting the battery may temporarily turn off the light.

A diagnostic computer can be used to pull the codes that trigger the lights, helping you determine the cause of the check engine light. If you are unsure why your Volkswagen check engine light is on, consult a certified technician at a Volkswagen service center.

Read also >> VW Check Engine Light Codes (Common Car Diagnose + More)

Read also >> Engine Malfunction Light for Volkswagen (Causes, Symptoms, Solutions)

Read also >> Volkswagen Check Engine Light and Gas Cap Issues (Do This!)

Common Reasons for a Check Engine Light in Volkswagen Diesel Engines

Here, we will discuss some of the most frequent causes of a check engine light in Volkswagen diesel engine vehicles.

1. Loose or Missing Gas Cap

The gas cap is responsible for keeping your fuel tank sealed, preventing gas fumes from escaping into the air or, worse, into your vehicle.

A loose or missing gas cap can trigger a check engine light when the fuel system tests itself to ensure it is sealed. Make sure your gas cap is tight to avoid any issues.

2. Malfunctioning Oxygen Sensor

The oxygen sensor, also called an O2 sensor, relays important information to your car’s electronic control unit (ECU), which can be thought of as your car’s “computer.” Sometimes the oxygen sensor can get covered with oil, dust, debris, or corrosion and simply fail.

This can cause the sensor to send incorrect information to the computer, triggering the check engine light.

3. Worn or Damaged Spark Plugs or Wires

Spark plugs ignite the air/fuel mixture in the combustion chamber of your Volkswagen. Although spark plugs and wires last much longer than they did in older vehicles, they will eventually wear out and need replacing.

Worn plugs and/or plug wires can cause the engine to “misfire” and trigger a check engine light.

4. Faulty Mass Air Flow Sensor

The mass air flow sensor measures the amount of air entering the engine to determine how much fuel is needed to run your engine efficiently.

When it malfunctions, you could experience reduced performance and lower fuel economy. A faulty mass air flow sensor can cause a check engine light.

5. Catalytic Converter Needs Replacement

The catalytic converter helps protect our environment by converting harmful carbon monoxide into carbon dioxide. When not functioning properly, it’s possible for a catalytic converter to cause a check engine light.

6. Broken Thermostat

The thermostat in your Volkswagen’s engine helps manage operating temperatures to avoid overheating. An incorrect reading from a defective thermostat can cause a check engine light to appear on your dash.

It’s essential to ensure your thermostat is in good condition to prevent engine damage from excess heat.

How to Fix a Check Engine Light in a Volkswagen Diesel Engine Vehicle

If you encounter a check engine light in your Volkswagen diesel engine vehicle, it’s crucial to address the issue as soon as possible to prevent serious damage. The team of service experts at Volkswagen service centers can diagnose, repair, and keep your Volkswagen running like new. Here are the steps you should take:

  1. Consult a certified technician at a Volkswagen service center.
  2. Have the technician use a diagnostic tool to read the stored codes causing the check engine light.
  3. Address the underlying issue based on the diagnostic results.
  4. Reset the check engine light using a diagnostic tool or VCDS.

Prevention and Maintenance Tips

To prevent check engine light issues in your Volkswagen diesel engine vehicle, consider the following maintenance tips:

  1. Regularly check and tighten your gas cap.
  2. Have your vehicle’s oxygen sensor inspected and replaced if necessary.
  3. Replace worn or damaged spark plugs and wires.
  4. Clean or replace the mass air flow sensor as needed.
  5. Inspect and replace the catalytic converter if required.
  6. Ensure your thermostat is in good working order and replace it if needed.

By following these maintenance tips and addressing any issues promptly, you can keep your Volkswagen diesel engine vehicle running smoothly and efficiently.

VW Flashing Glow Plug Meaning Not What You Think >> Check out the video below:


Understanding the diesel engine malfunction light and check engine light in your Volkswagen vehicle is crucial for maintaining the performance and health of your engine.

By staying informed about the causes behind these lights and addressing issues promptly, you can prevent serious damage to your engine and keep your vehicle running at its best.

If you ever encounter a check engine light or diesel engine pre-glow light in your Volkswagen, consult a certified technician at a Volkswagen service center to diagnose and resolve the issue.

Steve P.

Steve is an automotive technician, technical writer, and Managing Editor. He has held a lifelong passion for cars, with a particular interest in cars like the Buick Riviera. Steve is based in Boise, Idaho.

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