The duty of your check engine light is to report that your car is not working the way it’s supposed to be. When it turns on, it indicates your car is not running the way it’s designed.
It might also mean it’s producing higher-than-normal emissions. Whatever the reason behind, one thing’s for sure – you must turn that thing down.
In this article, we will discuss how to reset check engine light and some other essential things you should learn about.
Automobiles and Computer Advancements
Over a hundred years ago, cars were purely mechanical. Now almost all cars running on the roads have multiple computers inside that coalesce to make the car operational.
The primary computers you should look out are the transmission control module (TCM) and the engine control module (ECM), also called the powertrain control module (PCM). These two modules could be anywhere your vehicle depending on the model.
These two computers use numerous sensors to monitor multiple aspects of your vehicle. These includes transmission output shaft speed and engine coolant temperature to name a few.
More importantly, the ECM also monitors your engine and use the data gathered to do tasks like reducing emission or deliver more power.
The ECM can also detect issues like faulty airflow or out of sync data. When it finds a problem, it will activate the check engine light. It also simultaneously saves a DTC (Diagnostic Trouble Code) in the vehicle’s memory.
How to Reset Check Engine Light
If the light annoys you, there are a couple of options you can take to turn it off. Learning how to reset check engine light is actually an easy procedure as long as you have reliable instructions like the ones below.
1. Find and Fix the Problem
The most effective, yet the most basic thing you can do is to find the problem. The ECM is reporting something, and it’s your responsibility to do the next thing – the fixing.
When the ECM analyses the problem is already taken care off, it will simply turn its own light down.
For instance if you successfully fixed a loose gas cap, it will clear the DTC then turn the thing down. There’s a catch, though – the waiting game.
Each car model has its own standards or conditions for self-clearing DTCs. The thing is, it may take several days, even weeks before the ECM to self-diagnose the matter as “already fine” and finally turn off the CEL.
If you’re not a fan of waiting that long, you can take refuge to other methods of resetting the CEL.
2. Use OBD2 Scan Tool
Another way of resetting the check engine light, as well as clear codes, is to use a scan tool. The tool plugs into the On-Board Diagnostics Generation Two Data Link Connector (OBD2 DLC) port.
You can check your car manual to know its specific location; however, it’s likely this one can be found somewhere on the driver’s side.
There are various types of scanning tools, each differs in usage, capability, and cost.
Standalone OBD2 comes with a price tag ranging from below that of the USB cables up to a thousand dollars (or more).
If you just want a mere do-it-yourself operation, there’s no need to invest in the most high-end scan tools if your purpose is to use them only for reading and clearing DTCs and other fundamental diagnostic functions.
Now this one is similar to those used by both independent and dealership auto repair technicians. USB OBD2 can also be used to diagnose your check engine light by acting as a bridge between your car and a laptop.
You can use a laptop, connected to your car via USB OBD2, to operate the software needed to do the specified task.
Note: It’s not entirely advisable to use free software packages as you may have troubles along the way especially if you’re not fully adept.
On the other hand, paid OBD2 software can offer more control and more recommended if you don’t want to take risks.
Bluetooth OBD2 dongles
Now this one’s the smallest and the least expensive among other OBD2 Scan Tools. For this device to work, you must download an app first through your smartphone for it to communicate with your car.
It’s like a USB-type OBD2 but only through the use of a smartphone and an app instead of a laptop and a desktop software.
Comparable to the USB-type, it’s more advisable to go for paid apps rather than the free ones because they offer more control. Paid apps can also let you do live testing as well as view live data. However, free apps are enough if your purpose is to only read and clear your vehicle’s DTC.
You can choose one among the three OBD2 scan tool to proceed. So here are the steps to reset your check engine light using OBD2 Scan Tool.
- Regardless of what type you use, you must always turn your car OFF.
- Now attach the scan tool into the DLC (Data Link Connector).
- Do NOT start the engine but turn your key to the “on” position
- Now “connect” the smartphone app, laptop software, or the standalone tool.
- Now wait for a few minutes until the OBD2 is able to successfully connect and communicate with your ECM.
- Look for the functions “Erase Codes” or “Clear DTCs” and press/activate it. If you can’t find neither of the two functions, look for something similar or synonymous with them.
- Follow your software or app for specific instructions that came after your command.
- The scan tool should now confirm a successful operation
- After completing the tasks, turn your key to the “off” position
- Now wait for at least 10 seconds or more
- Try starting your car and observe the check engine light. It should now be off.
- Note: You can also follow the manual of your app or scan tool for specific instruction.
3. ECM Hard Reset
If the above two seems not to work as planned, your last resort is to do a hard reset. This procedure involves disconnecting your battery. Don’t worry though, it’s not as difficult as it sounds. Here are the steps to do an ECM Hard Reset
- Turn your car off
- Grab a ½-inch or 10mm wrench; or whatever size is needed for step 3
- Now disconnect the negative (-) terminal clamp of the battery
- Now the battery is disconnected, start depressing the brake for at least a minute. Note: This is to ensure no energy is left in the capacitors
- Release the break after a minute or two
- Reconnect your battery using the same tools in step 2
- Try starting your car after a few minutes and observe the CEL. It should now be off.
If the hard reset is successful, both the CEL and DTCs will be cleared. There’s a small chance ECM hard resets won’t work, especially if the ECM memory is not voltage dependent.
After the DTCs and CEL are cleared, you can expect your car not to “feel the same” for several days. That’s because the TCM and ECM will take time for it to fine-tune back to where it used to be.
Depending on your car model, you may do a procedure or enter a certain code first before you can start the car or turn on the radio. Further, some aftermarket alarm systems may activate their anti-theft mode.