Finding the best OBD2 scanner for VW and Audi can be a challenge.
Volkswagen Check Engine Light ON
In this guide, you will learn about Volkswagen Check Engine Light (CEL) and common problems that trigger the VW engine light to stay on.
You will also find step-by-step instructions on reading VW check engine light codes yourself using an OBD-II scanner.
What you may notice when your VW Check Engine Light stays on.
- VW Engine Running Rough
- Engine Misfire / Car Shaking
- Reduction or Lack of power
- Poor throttle response
- Unusual sounds from the engine
- Smoke from the exhaust
- VW check engine light blinking
- Engine idles high
A check engine light on your VW is indicating something is wrong with the performance of the engine.
- Faulty oxygen sensor
- Bad spark plugs
- Ignition coils
- Mass airflow (MAF) sensor
- EVAP leak such as loose gas cap
- Catalytic converter
- Vacuum leak
These are the most common problems that trigger the check engine light on a Volkswagen.
There are hundreds of possible problems that can trigger the check engine light on a Volkswagen. To find out why your check engine light is on, read the fault codes.
How to read Volkswgeen fault codes
Below you will find instructions on how to read VW Diagnostic Trouble Codes (DTC). Do not clear the codes without fixing the problem first.
What you will need
- Locate an ODB port in your VW - it is usually under the dashboard on the driver's side.
- Plugin your OBD2 scan tool and let it connect to the car. Turn the car ignition on so that your dashboard illuminates (don't turn the engine on).
- Scan for error codes. Store codes, or write them down. Research the codes and what could be causing the problem in your VW.
- Fix the problem.
- Reconnect the scanner and select Clear Codes to reset the VW engine light.
- Turn the ignition off and wait for several seconds. Turn the engine on and check to make sure the check engine light is off.
Common Problems Explained
The Check Engine Light on your Volkswagen (Jetta, Passat, Golf, Tiguan, etc.) can come on for many reasons, including defective mass airflow sensor, bad thermostat, engine temperature sensor, short in main wire harness, vacuum leak, worn spark plugs and failed ignition coils.
Let's take a look at some of the most common problems that cause VW check engine light to come on.
A loose gas cap can trigger a Volkswagen engine light to turn on. Make sure you tighten the gas cap until you hear it click. If you read the codes, still get a code for EVAP system leak, inspect or replace the gas cap.
Sometimes the seal can crack and not seal the fuel tank properly. You can drive the vehicle, and the light will reset after a few driving cycles. Or use an OBD2 Scanner to reset the codes yourself.
Worn spark plugs are another common problem that triggers VW check engine light to come on. Typically you should change your VW spark plugs at the 90,000-mile mark. Volkswagen owners often forget to perform this maintenance and end up with CEL coming on around the 120,000-mile mark.
Bad O2 sensors are another common reason VW check engine light comes on. The oxygen sensors on Volkswagen vehicles often fail in the 80,000 to the 100,000-mile range.
Volkswagens aren't the only cars suffering from oxygen sensor issues. Audi, BMW, Mercedes-Benz, Porsche, Toyota, and Honda struggle to make oxygen sensors that last forever.
Volkswagens are famous for ignition coils frequently failing in their four-cylinder 1.8 and 2.0T engines. In some cases, even a brand new ignition coil can malfunction or last less than 10,000 miles.
When VW ignition coils fail, the check engine light will flash on and off, the engine will shake, plus you will have poor throttle response. When reading the codes with an OBD2 scanner, you will get codes such as P0300, P0301, P0302.
Coolant Temperature Sensor
Volkswagen engine coolant temperature sensor can fail, triggering check engine light to come on. Replacing the temperature sensor is a simple DIY fix that many VW owners can perform at home.
If your Volkswagen check engine light is continuously ON, it can be due to hundreds of possible issues. You will need to read the codes with an OBD2 scanner. The problem can be something as simple as a loose fuel tank cap, a bad spark plug, but it can also indicate a serious engine problem.
VW Check Engine Light Flashing
When your Volkswagen check engine light is flashing, it means the onboard diagnostic system has detected a misfire. This is due to fuel not getting burned in the cylinder. This problem is typically caused by a bad spark plug or ignition coil. But it can also be an indication of a blown head gasket or clogged catalytic converter.
Flashing check engine light is a definitive sign of abnormal combustion. Never ignore your VW engine light or drive the car for an extended time, especially if your Volkswagen CEL is flashing.
Driving a Volkswagen with a flashing check engine light could have a devastating effect on your engine and catalytic converter. If the engine overheats, pull over and turn off the car. Never drive your VW hard or even moderately if your Check Engine light flashes.
Should I Drive with Check Engine Light On?
If your VW is still running fine with CEL on, in general, you can continue your drive. You should adjust your driving style, be moderate, and don't push it to high revs.
Pay attention to anything out of the ordinary regarding how your engine works, including warning lights on the dashboard. Look for smoke from exhaust, rattle or knocking from the engine bay or rising engine temperature.
If your engine displays any of the before mentioned symptoms, you should not dive it. Although you may travel a short distance, drives longer than several miles are an absolute no-no.
Frequently Asked Questions
Why is a check engine light in my VW on?
The car uses a Check engine light to warn you that something is not working properly. Problems are usually related to fuel injection and ignition system or emission control systems.
Can I drive my VW with a Check engine light on?
A check engine light on its own doesn't mean that you have to stop and call the tow truck. If your car runs normally, you can drive your car. Have it checked as soon as possible, though.
So, if your VW runs rough, misfires, or emits black, white, or blue smoke from the exhaust, you should not drive it.
What does a flashing Check Engine light on my VW mean?
Flashing Check engine light indicates misfire. This is very damaging for your engine and catalytic converter. Immediately ease off the throttle, as this will likely stop the misfire. If the flashing continues, pull over and turn off the engine.
Why is my VW check engine light on and off?
If your Check engine light is blinking ON and OFF, this means you have a misfire. A misfiring engine will damage your catalytic converter quickly, so immediately ease off the throttle. If this does not stop misfire, pull over and turn off the engine.
How can I access error codes on my VW's board computer?
Unfortunately, error codes can not be viewed through a board computer. The only way to read the stored codes is by using a scan tool. You can visit your dealer or an independent workshop, or you can buy your own scan tool.
Are all scan tools expensive?
If you search for scan tools, you will find various scan tools with a hefty price tag. This is usually professional equipment. As an amateur or DIY, you can go with cheaper and simpler versions. If you have a smartphone, Bluetooth ODB2 readers are the best option. They are very cheap, small and easy to use.
How can I know what the error codes mean?
Depending on the scan tool you have, you usually get a code without any written explanation. Especially if you have a cheap scan tool, yet, this is more than enough. Just search that code and your car on the internet or forums.
What does the VW check engine code p0411 mean?
Error code P0411 indicates Incorrect Flow in the Secondary Air Injection System (SAI). This is an emission control system that uses an air pump to flow fresh air into the exhaust system. Usual failure points are pump, hoses, or check valve. A damaged exhaust system can cause this error, as well.
VW check engine light, no codes?
If you have a Check Engine light, but there are no stored codes, this usually means that your scan tool can only read generic powertrain codes. This is usually the case with cheaper OBD2 readers. VW has additional specific codes that can be accessed by more specialized scan tools.
What could cause VW check engine light after an oil change?
An oil change can not cause a Check Engine light. If it came on immediately after the oil change was done, probably some sensor or connector was unintentionally unplugged during this process.