Reset check engine light

When it comes to the reset check engine light process, there are not as many options today as there use to be. Before the invention of OBD 2 resetting your check engine light was a simple matter of disconnecting the battery.

OBD II was deployed in 1996. If your vehicle is newer than that I do not recommend that you disconnect the battery for resetting the light.

But stick with me I will explain how to reset check engine lights by disconnecting the battery below on this page. As a Certified professional auto mechanic it is my duty to let you know what could go wrong first!

Remember if you have a hard failure the light will come right back on. Consider pulling the codes and following a repair manual diagnostic chart for the specific code set to solve the issue properly.

Another reason for not disconnecting the battery is that newer vehicles have a few installed options on-board that require constant battery voltage.

I know what your thinking, what if you have to replace the battery or disconnect it for cleaning and or maintenance. I personally use a device called a battery tender. This is plugged into the cigar lighter socket before you disconnect the power and ground cables to help keep the on-board memory alive.

Reset check engine light complications

When the power is disconnected to reset the check engine light your radio will think that it is being stolen. The radio will go into a self defense mode and not operate until a special code has been inputted.

In most cases, this special code is included in your owner's manual. Or was supplied by the dealer at the time of delivery, which may not do you any good if you have purchased this car used.

Also if your vehicle is equipped with a factory installed car alarm or theft deterrent system disconnecting the battery may cause a few problems with this system as well.

The owner’s manual may provide a procedure for replacing the battery and disabling the alarm system before the battery is disconnected. Some car makers provide a sleep mode for just this operation.

And last but not least stored in the computer along with the code is the vehicles learned memory. This stores driving habits like shift points and IAC steps for idle control.

The vehicle may have stalling and hard shifting problems for a while after the battery is reconnected. It will recover and re-learn but it may take several drive cycles.

They are able to do this without disconnecting the battery or causing any of the problems mentioned above. One of the best selling automotive scanners on Amazon is the Actron.

Click on the product and take a look at the customer reviews on this item. The actron 9180 is capable of reading the data stream and may be overkill if you just want to reset the check engine light. If this is the case the cheaper equus 3030 is below.

Reset check engine light the hard way

Most vehicles from 1996 and newer have a stay alive memory built-in to the computer system. When you disconnect the battery from the vehicle to reset the check engine light. The computer will be able to hold the memory and the code for several minutes and in some cases several hours.

Battery voltage is stored in a capacitor and is supplied to the computer to keep the memory alive. The way around this is to disconnect the battery and then hold down on the horn button.

This will drain the small electrical current that is stored in the control modules capacitor. This will reset check engine light on most models.

As a side note, when you do this you will be erasing all memory associated with the computer as well.

When you reconnect the battery on the vehicle and confirm the reset check engine light procedure has been successful, you may find that the engine idle may be erratic for several drive cycles.

This is because the memory idle learn has also been erased along with your check engine light code. This problem is usually short-term and will correct itself, after driving the vehicle for a few miles at highway speeds.

So to review you do have a few options for resetting your check engine light, but the easiest way is to use an auto scan tool to clear the code.

To the left is one of the cheapest scanners on the market. The equus 3030 works great but It reads and erases codes only.

This is much better then disconnecting the car battery. Using the automotive scanner tool will avoid any and all of the above-mentioned problems.

If you are interested in a scan tool that can do more you can visit my automotive scan tool reviews page.


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On my auto scan tool homepage you will find a few more articles about the diagnosis of check engine lights. Plus more on the reset check engine light procedure using scan tools


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