Canceling CEL in 99 Miata

Is a scan tool necessary to cancel the light and codes after the repair? If not, what is the procedure?

You could disconnect the battery.

Keith Tanner wrote: You could disconnect the battery.

That's what I was thinking

I thought about that, but read that doing that shuts the light off but doesn't remove the codes. I don't know if that is correct or not. I also didn't want to lose the settings in the head unit. I removed the EFI fuse, which has always worked on my Hondas, but it didn't work on this car.

Then you use your scanner. You DO have a scanner, right? They're cheap now.

The ECU has both constant and switched power. You may have pulled the fuse for the switched power.

Grab one of these:

http://www.amazon.com/Scanner-Engine-Reader-Checks-Diagnostics/dp/B014RG5B74/ref=sr_1_1?s=automotive&ie=UTF8&qid=1450812866&sr=1-1-spons&keywords=obd2+scanner&psc=1

Download an app called Torque. Plug it in, pull the code, then clear it using the app. Super super easy and well worth the money.

come pick up that atv axle and i'll plug my scanner in and clear your codes and make sure all is well.

First, thanks for the help, guys. Second, I don't have a scanner, as I rarely need one. If I did I wouldn't be asking these questions, right? I can take it to oriellys down the road and have them do it. i was just curious to know what was necessary to cancel the codes, as there is a lot of controversy about it on the net. Even here nobody seems totally sure about what is needed to cancel the codes.

It's easy. I'm not sure why you think there's confusion or controversy.

Disconnect the battery or use a scanner. The guys at oreilly's should be able to do it.

And at $17, I consider a scanner to be a required part of anyone's toolbox. It'll help you work on any car that's been made in the past two decades. I keep one in my bag along with a Leatherman and a flashlight, it's that basic a tool.

In reply to Keith Tanner:

I'm not confused at all. I just commented that nobody seemed completely sure about what disconnecting the battery does versus using a scanner ( a question that really still hasn't been answered definitely). I'm not sure why you seem to have your panties in a knot about it though. I'm a former NIASE (now ASE) master technician. I have every tool under the sun, but I quit wrenching for a living before scanners were available. You may think it's necessary, but I dont. I need one about once a year, and when I do I have to go to the auto parts store anyway to get the parts to do the repair, so it's really no problem to have them do it.

Disconnecting the battery does clear the codes. This may not be the case with other vehicles, but it's the case for a 1999 Miata. I didn't go any further into that because it wasn't something you wanted to do due to the radio memory, so I didn't realize it was still under discussion. I could pull the wiring diagram out to find out exactly what the fuse is that kills the ECU memory if that's important.

Disconnect the ECU connectors

Its really a question of the age of the car. Most anything built up to 00 will clear ECU codes with a battery disconnect. Airbag or ABS codes are less likely to disappear- they seem to have some battery backup, or something that doesn't need power to remember. As stuff gets newer, they almost all will have some sort of memory retention. Long term disconnect might work, but long term is weeks, not days.

Drive the car, it will go out on it's own after a while.

Not necessarily . Depends on the code.