When you have your check engine light and take your car to the mechanic or dealership, you expect that the light will go away after they work on the problem. Unfortunately, the light may still be back on after repair.
So, why is your check engine light back on after repair? Your check engine light is back on after repair simply because the underlying problem hasn’t been fixed, due to improper repair, or they forgot to clear the code from the computer after repair.
Read on to discover possible reasons why your check engine light is still blinking after a repair, how you can fix it, and other helpful information you need to know about this issue.
Why check engine light is back on after repair
It is not uncommon for the check engine light (CEL) to come back on after repair. The simplest explanation for this issue is that the initial cause for the engine light to come on hasn’t been fixed.
After all, the light illuminates when there’s a problem that needs fixing and goes away once it has been taken care of.
It could be that the mechanic didn’t fix the issue at all or didn’t fix it correctly (i.e. only handled part of the repair). most mechanics and dealerships have a tendency to fix only the specific issue the customer has brought forward.
They don’t go into the depths of downloading all the stored error codes which will enable them to establish all the problems ailing the vehicle.
You can avoid this by having a mobile mechanic do a complete check engine light inspection before going to the dealership or mechanic shop. This will give you a clear picture of problems ailing your vehicle, what’s causing the issues, and what needs to be worked on.
This will save you a lot of time and money and dramatically reduce the chances of the light coming on after you’ve visited the repair shop.
That said, you should consider taking your car back to the mechanic or the auto shop that worked on it immediately. And if they can fix the issue, you can take it to another more competent place for re-diagnosis and fixing.
The check engine light may also have come on again due to a completely different problem than the one your car got fixed for. Remember, modern vehicles have thousands of diagnostic error codes representing countless vehicle functions.
To confirm if the check light is on because of the old or a new issue, you should consider having the codes read again.
It could also be that the vehicle has been repaired correctly but the check engine light is taking a while to go away.
Sometimes the CEL may go away only after you drive for a given number of miles. Other times, the vehicle computer may take a while longer to recognize the new part.
Why is check engine light came back on after replacing O2 sensor?
If you’re still seeing the check engine light after replacing the oxygen sensor, this is your part.
One possible explanation for this issue is that the sensor wasn’t the issue. You might have replaced an O2 sensor that was in perfect working condition for no good reason.
Most car owners blindly follow the OBD II codes, not knowing that these don’t offer specific solutions but only offer suggestions (usually a list of 4-5 suggestions) of what could be wrong with your car.
The codes will only help give the mechanic suggestions on where to start looking when trying to solve the problem.
A reputable mechanic shop will employ their diagnostic skills to find out the root cause for the engine light rather than just replace the O2 sensor based on the diagnostic trouble codes they get.
In most cases, the oxygen sensor itself isn’t the problem and doesn’t need to be replaced. The code could simply be meaning you need to check the sensor.
The problem could be a wire running from the sensor to the electrics connection, the connection where your sensor is screwed to the exhaust pipe might be rusty, or road debris may have bent the exhaust pipe or the point where the O2 sensor is connected.
Or it could be none of these issues!
Before you get down to getting a new oxygen sensor for your vehicle, make sure that you indeed have a bad oxygen sensor that needs to be replaced. You would be surprised it’s not the sensor that’s the problem but another factor altogether!
Why is check engine light back on after replacing catalytic converter
The light is back probably because the catalytic converter wasn’t the problem and didn’t need to be replaced.
In fact, the car could be experiencing an issue that’s completely unrelated to the catalytic converter.
It’s advisable to have a mechanic pull the error codes for you so you can see what the problem is. If the scan tool still brings up catalytic converter code, then there could be other failures tripping the code.
Other possible problems bringing up this code include a faulty oxygen sensor, exhaust leak, etc.
It could also mean that something else got damaged during the replacement process or the mechanic forgot to replace the code after the replacement.
The surest way to know why the light doesn’t go off is to have the codes read by a reputable repair shop or dealership to determine the exact problem facing your vehicle.
How long does it take for a check engine light to go off after repair?
There’s no specific time after which the check engine light clears off after repair. That said, the check light may go off in a short while, with just a drive cycle after repair.
Other times, the codes will clear and the light go off after several drive cycles, say 10 to 20 cycles. Some vehicles will require to drive them for about 50 to 100 miles for the codes to clear.
Sometimes, the light may hang around for a little longer but will eventually go off provided all the issues with your car have been fixed and there are no new problems affecting it.
Overall, the specific time will vary depending on the type of data that offset the engine light in the first place.
Your mechanic can also manually clear the codes and switch off the light. But if the underlying problem hasn’t been fixed, the light may come back on—though not immediately.
How far do you have to drive to reset the check engine light after repair?
In most cases, you’ll need to drive your car between 50 to 100 miles for the codes to clear up and the check engine light to switch off.
During this driving period, the onboard computer will be monitoring all the system sensors and then register the results.
However, the CEL reset can happen automatically after taking your car through 10 to 20 drive cycles. A single drive cycle involves turning your car on and then turning it off again.
Nevertheless, if the issue affecting your vehicle hasn’t been cleared, you can rest assured that the light will not go away after the computer runs diagnostics for its sensors once more during the driving period or the drive cycle phase.If you’re experiencing a check engine light after repairing your vehicle, there could be several reasons behind it. One possible cause is a malfunctioning sensor, which can trigger the check engine light to come on even after the repairs have been made. However, if you have already checked the sensors and the light is still on, you may want to consider other causes, such as issues with the fuel system or other components of the engine. Our articles on troubleshooting check engine light issues can provide valuable insights into the problem. For example, if you experience a check engine light after filling coolant, our article on after filling coolant may be helpful. This article covers common causes and solutions for check engine light issues that arise after filling coolant. Similarly, if you’re experiencing a check engine light after changing your transmission fluid, you may want to read our article on after transmission fluid change. This article discusses potential causes and solutions for check engine light issues that arise after changing your transmission fluid. Take a look at these articles for expert advice on diagnosing and fixing check engine light issues.
1. Does check engine light turn off automatically after repair?
It depends. Sometimes the light will go off automatically after the problem has been solved. Other times, the check engine light will only go off after you have driven your vehicle for a given number of miles. In some cases, the vehicle computer may require more time to recognize the new part.
2. Will the check engine light go off by itself after repair?
Yes, the check engine light may go off by itself after repair after a specified drive cycle and after all the monitors are run. However, the light may hang around until you manually erase the logged OBD codes using the OBD 2 scan tool.
The check engine light not going after repair usually means that the mechanic shop didn’t repair the underlying issues or they may have partly worked on the issue and not solved all of it. There could also be other problems affecting your vehicle
In either case, we advise you to take your vehicle back to them as soon as possible. Or you should go to a more competent repair shop where they’ll diagnose it for the actual problem affecting causing the light and fix it.
Hopefully, this article has answer all your questions on why check engine light doesn’t go away after repair, all possible causes, and most effective ways to solve the issue.