We’ve scanned over 398956 Audi A4s with the FIXD OBD2 scanner and app. These are the 5 most common reasons for a check engine light in your Audi A4.
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| Code | Severity | Description |
|---|---|---|
| P0299 | LOW – Continued driving for a short period of time is okay | The turbocharger is not providing as much power as expected. This puts the engine into limp mode |
| P0302 | LOW – Continued driving for a short period of time is okay | Cylinder number two is experiencing misfires |
| P0303 | LOW – Continued driving for a short period of time is okay | Cylinder number three is experiencing misfires |
| P0420 | LOW – Continued driving for a short period of time is okay | Your catalytic converter isn’t functioning efficiently. This could increase the output of harmful pollutants. |
| P0301 | LOW – Continued driving for a short period of time is okay | Cylinder number one is experiencing misfires |
When To Expect These Codes With Your Audi A4
We’ve scanned millions of cars so we know at what mileage these common problems usually show up. Sometimes they happen sooner than expected or not at all, but these problems usually appear by the following mileages:
- P0299 usually appears after 134491 miles
- P0302 usually appears after 160361 miles
- P0303 usually appears after 162886 miles
- P0420 usually appears after 174996 miles
- P0301 usually appears after 161187 miles
Check Your Gas Cap
One of the most common reasons for a check engine light in your A4 is also the easiest problem to fix. A loose gas cap is often the reason the check engine light turns on. This happens because the engine detects a leak in the evaporative emissions system, which exists when the gas cap isn’t tightened until it clicks. It’s easy, and it’s free!
What Should I Do If the Check Engine Light Is On in My A4?
There are many issues that can trigger the A4 engine light, from a loose gas cap to major engine issues. If this light turns on, don’t panic. Check out our guide on what to do when your check engine light comes on. Following this guide can help you avoid driving with a serious problem and causing more damage to your engine.
If you’d like some more information on diagnosing a check engine light yourself, you can also check out our article on the most common reasons for a check engine light.
For those of you who prefer a mechanic, you can find a trusted repair shop for inspection easily with RepairPal.
> Find a RepairPal Certified Shop Near You
What the Check Engine Light Means
Your A4’s check engine light is part of the onboard diagnostics system (OBD2). All gas-powered cars and trucks made since 1996, plus diesel cars and trucks since 2008, have a diagnostic system to manage the engine and monitor emission system performance. It alerts the driver to any problems by turning on the Check Engine Light on your dashboard. Special tools known as OBD2 scanners or car code readers can access diagnostic information from this system to find out what’s wrong with your car and how serious the problem really is.
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How to Read Your A4’s Check Engine Light
There are a few ways you can read the diagnostic trouble code stored in your car’s computer.
1) Go to your local mechanic. They will plug in their professional scan tool to read the code and identify the cause of the problem. This won’t help you on the side of the road, however, and they will charge a fee for this service. You also may not have a shop that you trust to diagnose the problem accurately, rather than try to make some extra money from repairs.
2) Go to a nearby auto parts store. Most parts stores will plug their OBD2 scanner into your car and give you the problem code and description at no charge. The person providing this service is likely not a mechanic, and may not be able to provide any more information than just the code and its technical description. It’s also possible that they may try to sell you products you don’t need in order to “fix” the problem.
3) Read your own check engine light codes with or without a scanner. Checking codes manually can be done but, it’s tedious. Borrowing a scanner or buying one makes the process easier. There are many OBD2 scanners you can buy that will read codes and provide other engine information anytime you want. FIXD is able to translate any A4’s check engine light trouble code into plain English directly on your smartphone.
How the FIXD Check Engine Scanner Works
The FIXD car scanner plugs into your car’s OBD2 port. This is a trapezoid shaped plug located under the dashboard on the driver’s side of the car. Read more about how to find your OBD2 port on your particular car.
The FIXD Sensor and free mobile app will tell you in plain English what problem codes exist. You will get a detailed description of the problem so that you can make informed decisions about repairs.
Understand Your CEL
FIXD instantly translates over 7,000 error codes into simple terms right on your phone.
See How Serious Your CEL Is
Learn if your problem is serious or not, and whether it’s safe to keep on driving.
Get Maintenance Alerts
FIXD can automatically alert you when your A4 is due for an oil change and other routine maintenance, based on your specific model and its mileage.
Monitor the Health of Your A4
If your check engine light turns on, FIXD will immediately send a notification to your phone. You can also monitor data in real time, such as oxygen sensor voltage, fuel trims, vehicle speed, and more.
Is It Safe to Drive with My Check Engine Light On?
That depends on what problem triggered the light to come on in the first place. You will need to use an OBD2 scan tool like the FIXD Sensor to find out exactly what’s wrong, how severe the issue is, and whether or not it’s safe to keep driving.
Generally speaking, if the indicator is a steady yellow light, it should be okay to keep driving.. This could be something like an emissions issue. While your car will keep running just fine, it’s still best to get this diagnosed and repaired sometime soon, especially if you live in a state that performs vehicle inspections.
If the light is blinking, you should stop as soon as it’s safe to do so. This indicates a serious problem, such as a misfire, that is occurring right then. It’s also good to check for low oil or overheating. If your A4’s check engine light is red, you should stop driving immediately.
If your A4 experiences driveability issues, such as reduced power, slow down and take it easy on the engine to avoid making the problem worse.
How Can I Reset the Check Engine Light in My A4?
If you have resolved the problem, you may want to clear the codes that triggered your A4 engine light. If you reset the light, drive, and it doesn’t turn back on, your problem is fixed.
The easiest way to reset the check engine light on your A4 is with FIXD. While auto parts stores will typically read your codes for free, they will not reset the light for you, and shops may charge more than $100 to do this.
In the FIXD app, you can reset the light anytime you want for free. After performing the engine scan, go to the Details page and click the “Clear Engine Light” button. The light will turn off, and any codes stored inside your A4’s computer will be cleared. If the light turns back on after a few miles of driving, the issue likely still exists.
Diagnose Your A4’s Check Engine Light with FIXD
If the check engine light turns back on, use FIXD to get detailed engine diagnostics, plain English code descriptions, issue severity warnings, and so much more. Learn more about the FIXD Sensor and mobile app today!
At FIXD, our mission is to make car ownership as simple, easy, and affordable as possible. Our research team utilizes the latest automotive data and insights to create tools and resources that help drivers get peace of mind and save money over the life of their car.
