Audi Check Engine Light ON A1 A3 A4 A5 A6 A7 Q3 Q5 Q7 TT

Audi Check Engine Light ON Troubleshooting

Updated Friday Mar 16, 2018

If your Audi Check Engine Light (CEL) is ON don't panic. The problem may not be as severe as you may think. When Audi CEL turns on be that an A1 A3 A4 A5 A6 A7 Q3 Q5 Q7 TT, it means that a fault code (Diagnostic Trouble Code / DTC) is stored in the Engine Control Unit (ECU). No need to schedule an appointment with your mechanic to diagnose CEL when it is so easy to read the codes yourself. Retrieving Audi check engine codes is so simple that you can perform in your driveway. You need a Level 1 OBD-II scanner some of which cost as little as $15. Take a few minutes to read this guide to learn about the common problems that can trigger Audi CEL and how to diagnose the problem yourself.

The cause of Audi check engine light can be something as simple as a loose gas cap to a sign that a serious engine or transmission problem is underway.

audi check engine light


Common causes of Audi Check Engine Light include:

  • Loose Gas Cap ( No symptoms)
  • Oxygen Sensor
  • Worn spark plugs (Engine misfire)
  • Ignition Coils / Coilpacks (Engine shaking)
  • Vacuum leaks (Intake Air System Leak from cracked and loose hoses)
  • Bad catalytic converter (Catalyst Efficiency Below Threshold)
  • Low-quality gas
  • Turbo Problem
  • Ignition Control Module

If your Audi check engine light comes on and there are no other symptoms, the first thing that you should do is tighten the gas cap. If gas cap triggered the check engine light, within two to three days of normal driving the light will reset itself. No need to use a scanner to reset the light. If after a couple of days the CEL remains on you will need to read the codes. Don't ignore Audi CEL even if the car drives fine. Follow the instructions below to learn how to read and clear Audi fault codes from the Engine Control Unit. 

Audi Check Engine Light Flashing

If your Audi check engine light is flashing it indicates that there is an engine misfire. We would not recommend driving an Audi if the engine is shaking. It is better to have the car towed to prevent serious engine problems. If your Audi CEL light is flashing, it indicates that the problem is more serious. Under these conditions, the car may also go into limp mode.

audi check engine light on due to bad spark plug ignition coil pack A1 A3 A4 A5 A6 A7 Q3 Q5 Q7 TT

Audi shaking is often caused by a worn spark plug, bad ignition coil, Ignition Control Module (ICM), or bad catalytic converter.

Read Codes / Reset  Audi Check Engine Light

Reading and clearing Audi check engine light is very simple. Don't clear Audi check engine light without fixing the problem. You need to figure out why the CEL turned on. Once you find what caused CEL to come on, fix the underlying problem. Often we see people disconnect the battery or use a scanner to clear Audi check engine light. Clearing Audi check engine light does not solve the problem. The light will come back on within a few days if the problem isn't fixed. In fact, if you fix the problem that caused your Audi check engine light to come on but didn't clear the light, the CEL will reset on its own typically within 5 or 6 driving cycles.


To read Audi check engine light as outlined in this guide, you will need an OBD-II Scanner. Any scanner on the list will be able to retrieve the fault codes. Scanners that are designed specifically for Audi such as Audi VAG COM Scan Tool will provide more accurate descriptions. 

Step 1

Locate OBD-2 port under the dashboard on the driver's side. This is a 16-pin port. All 1996 and newer Audi vehicles have this port.

Step 2

Audi Check Engine Light ON Troulbeshooting

Plug in your OBD-2 Scanner into the OBD2 port.

Step 3

How to diagnose Audi check engine light service engine soon A1 A3 A4 A5 A6 A7 Q3 Q5 Q7 TT

Turn key to position II. All the dashboard lights will turn on. Do not start the vehicle.

turn audi on to read codes check engine light related

If your Audi has Start/Stop button you will need to press the Start button without pressing the brake pedal.

Step 4

Check Engine Light On Audi

Allow the OBD2 scanner to turn on and connect to your Audi Engine Control Unit (ECU).

Step 5

Read Audi check engine light codes from the Engine Control Unit (ECU)

Audi CEL Repair Cost

Average cost to fix Audi check engine light can range from $150 to $500. It is difficult to determine the exact cost to fix Audi check engine light without pulling the codes first. If you take your car to the mechanic, there is a diagnostic fee (reading codes from the ECU which you can also perform yourself) and the repair fee which depends on the problem. Auto parts stores such as Auto Zone or Advance Auto Parts may scan the codes for free. 

If you call any Audi mechanic they will ask you to bring the car in for a check-up. Or you can get an OBD-II scanner and retrieve the codes yourself. Even if you don't plan on fixing the problem yourself, you will have a better idea of what is wrong. Once you retrieve the codes you will know if the problem is a loose gas cap or an expensive repair. Sometimes it can be challenging for a shop to diagnose the problem because the issue can be intermittent and can not be duplicated when you are at the shop. If you have a scanner with you, plug it into the OBD-2 port and retrieve the codes when you experience the problem. 


Check Engine Light Flashing

If your check engine light is flashing it means that the engine control unit has detected a misfire. You should stop as soon as possible and have your vehicle towed if necessary to prevent further damage to the engine or catalytic converter. 

What this means is that one or more of your cylinders are not working properly. This can be caused by a number of things such as bad spark plug, faulty ignition coil, bad ECU, clogged catalytic converter. 

If your car is flashing the check engine light and you continue to drive, you can damage the engine or the catalytic which can cost anywhere from $800 to $1500 to replace.

Top 10 Causes of Check Engine Light

Here is a list of the most common causes of Check Engine Light. Average costs to repair these problem has been included. Please note that for high-end vehicles the repair cost can be outside of this range. The repair costs shown below are typical prices you will pay at the dealers and auto repair shop. When a DIYer performs these repairs the average cost is significantly lower. 

  1. Oxygen Sensors 
    • Repair Cost: $200-$400
    • Repair Difficulty: Easy 
  2. Catalytic converter
    • Repair Cost: $750-$1500
    • Repair Difficulty: Moderate 
  3. Spark Plugs
    • Repair Cost: $250-$600
    • Repair Difficulty: Easy
  4. Loose Gas Cap
    • Repair Cost: Free - $25
    • Repair Difficulty: Very Easy
  5. Mass Air Flow MAF Sensor
    • Repair Cost: $200-$400
    • Repair Difficulty: Easy
  6. EVAP Purge Control Valve
    • Repair Cost: $120-$400
    • Repair Difficulty: Easy
  7. Ignition Coils
    • Repair Cost: $140-$600
    • Repair Difficulty: Easy
  8. Thermostat
    • Repair Cost: $200-$650
    • Repair Difficulty: Moderate
  9. Camshaft Position Sensor
    • Repair Cost: $150-$400
    • Repair Difficulty: Easy
  10. Fuel Injectors
    • Repair Cost: $350-$650
    • Repair Difficulty: Easy

Important Notes

  1. Clearing the check engine light using a scanner or by disconnecting the car battery does not fix the problem itself. Clearing codes without fixing the problem simply erases the codes from Engine Control Unit memory. Also keep in mind that if your car requires an emissions test soon after you clear the code, you will fail the emissions test. Clearing (CEL) codes also set the emissions readiness indicators to NOT READY. The car will require a few days of driving or a specific drive cycle to test all the emission systems and set them to READY.
  2. We recommend that you get a second opinion from a professional before you replace any parts. Do not replace car parts based on the fault code alone. It is important to consider the symptoms and the code before you come to a conclusion. For example, you may get a code for a bad oxygen sensor. While the oxygen sensor can surely be defective, a code for oxygen sensor can also be triggered by a cut wire, bad connector,  bad catalytic converter etc. Keep in mind that even a mechanic may have a difficult time diagnosing those rare cases. 
  3. If your check engine light turns on while driving continually monitor the engine temperature and oil pressure light. If any of these lights turn on, safely pull over and turn off the engine. 
  4. Do not ignore the Check Engine Light warning. Diagnose your vehicle as soon as possible.
  5. Auto parts stores such as Advance Auto Parts or AutoZone may offer free scanning of the Check Engine Light. 
  6. Check Engine Light (CEL) may also be referred to as Service Engine Soon (SES), malfunction indicator lamp (MIL). 

Frequently Asked Questions

Yes, disconnecting the battery usually clear the ECU codes. By turning the check engine light off this way you will not fix the problem. If you believe the check engine light needs to be off, drive the car for a few days and the CEL will reset itself. The Onboard Diagnostic System in your car continually monitors your vehicle and will turn off the CEL if the problem is solved. If the problem hasn't been resolved, even if you disconnect the battery, the CEL will come back up again which can be as soon as you restart the car or up to a few days.

If check engine light is on, it will not pass emission inspection/smog test. If the light was recently reset with an OBD2 scanner or by disconnecting the battery, you need to drive the car for a couple of days for the systems to be ready for testing.

It could be because you are using an OBD2 scanner that does not support the protocol used in your car. Try a different scanner. Also, there may be an issue communicating with the ECU due to a damaged wire or ECU malfunction.

No. The check engine light is not the reason why the car doesn't start. If the car doesn't start, read the codes and maybe the CEL will give you a code that can help you diagnose the car. Clearing codes will not make your car start.

It may be just bad timing. An oil change is not going to trigger the CEL. Unless MAYBE a sensor got accidentally unplugged, disconnected or damaged during the oil change. Take your car back to the auto repair shop that changed your oil and have them diagnose the problem.

No, the CEL should not turn on after routine maintenance. If you modified your engine, transmission, exhaust, intake, fuel system or other systems it can affect engine and emission control system, causing check engine or service engine soon light to come on. CEL should not come on if you changed tires or tire size.

Drive the car for a couple of days and allow the ECU to reset itself. If the CEL still remains on, read codes.

The check engine light is trying to tell you that there is a problem with your engine. It could be low coolant, stuck thermostat, transmission not shifting. Figure out why your car is overheating first and address that problem. DO NOT CONTINUE TO DRIVE IF YOUR CAR OVERHEATS.

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Posted by Erin T. on Apr 21, 2018 @ 21:03 pm