The Miata Key/Seatbelt Buzzer FAQ

by Stephen Foskett -

2.1 (10/03/03)

Q) What's a "key/seatbelt buzzer" anyway?

A) The U.S. Government requires all new cars sold in the United States to include a buzzer to notify the driver that their seatbelt is not buckled. Most US cars also use this buzzer to let the driver know if they leave their keys in the ignition when the doors are opened. Therefore, Mazda kindly equips all American and Canadian Miatas with just such a buzzer.

Mazda labels this device the "sound warning system" on the car's schematics. It's located in section Z, page T of the Miata shop manual.

Q) Can you describe the M1 buzzer?

On M1 cars ('89-'97), the buzzer is located above the drivers' left knee. It's a box with an 8-wire harness attached to the bottom of it. This harness has a distinctive cutout (see below) and little tabs to keep it in its socket. 6 of these wires are used. The pinout is as follows:

Ignition Door NC
Ground Key Belt Out Belt In NC
The six wires used are:
Black/yellow striped wire. When the ignition switch is on, this should have +12V on it.
Red/white striped wire. With any door open, this should be continuous to ground. With all doors closed, it is not.
Black wire. This should always be continuous to ground.
Blue/yellow striped wire. When the ignition key is inserted, this should have +12V on it. This is how the buzzer "knows" if the key is in the ignition. Any voltage greater than about 9V will cause it to trip. This terminal is used in the "light minder" modifications found below.
Belt Out
Blue green wire. This goes to the warning light on the cluster. With the ignition switch on and the driver's seatbelt buckled, it should have +12V. Otherwise it should be at 0V.
Belt In
Blue/white striped wire. This is connected to the switch on the driver's seatbelt buckle. With the ignition switch on and the driver's seatbelt buckled, it should have +12V. Otherwise it should be at 0V.
These connections are unused.

Q) Can you describe the M2 buzzer?

On M2 cars ('98-'05), the buzzer is located in the same place, but it sounds different. Instead of buzzing, it beeps. To disconnect it, unscrew the plate below the steering column. There is a phillips screw above each of your shins! Pull the plate down and then forward to remove it. Look above your left knee for a two-wire connector and disconnect it. There is a little tab to push to release it. I tucked this into another harness on my '03LS to keep it from rattling around. See Jeremy Pursley's site for more information and pictures.

Q) Why would I want to disconnect this handy buzzer?

A) Well, many people are annoyed by the sound of it, and some like to play their car radio while working on the car and don't want the Miata to hum along whenever the door is open. If you like the buzzer, or if you think it's important, leave it connected!

Q) I hate noise! How can I disconnect the whole thing?

A) You can disconnect the buzzer unit under the dash. Follow these simple instructions:

  1. Put the key in the ignition
  2. Open the door
  3. Stick your hand under the dash just to the left of the steering wheel
  4. Grab the rectangular plastic boxes until you find one that vibrates and makes the buzzer change pitch when your hand is on it
  5. Find the latch for the wiring harness
  6. Squeeze the latch open and pull out the harness
  7. Use a twist tie or some tape to fasten the harness/wire out of the way
  8. Enjoy!

Q) Is there an easy way to disconnect it temporarily?

A) If you unscrew the door plunger switches slightly, the buzzer will stop. Just screw them back in when you're done. This also causes the interior light to go off.

Q) I don't like wearing seatbelts and prefer to fly out of my car in a crash! How about just disconnecting the seatbelt alert?

A) There is a two-wire connector on a pair of wires running from the driver's seatbelt buckle under the seat. Put your hand under the driver's seat and you should find it fairly quickly. It's a pretty big connector for just two wires. One wire should be blue and white striped and the other should be black. You can disconnect this connector to stop this alert from working.

Q) How could I lock my keys in a car with no top? I just want to disconnect the key reminder!

A) Open the metal trim plate under the steering column. Note that this is the large, horizontal metal plate, not the trim around the key switch itself. Near the ignition switch are some wires leading to a connector with some more wires coming from it. This is called the "Key Reminder Switch" according to the Mazda Service Manual.

On cars with manual transmissions, this will be a two-wire connector with one blue/yellow wire and one blue/red wire. On cars with automatics, this will be a four-wire connector with blue/red, white/green, blue/white, and blue/yellow wires. On my car the connector is black, but other cars have white connectors.

Unplug this connector and the alarm will no longer sound when the door is open with the key in the ignition. At least on my car this also stops the seatbelt warning buzzer from working.

Note that leaving this connector unplugged on cars with automatic transmissions will have unknown consequences, so automatic owners should be careful about doing this! I imagine that this would be connected to some sort of lockout to keep the car from starting in gear.

Q) Can I damage anything in the car by doing any of this?

A) I won't guarantee that nothing will be damaged, but many Miata owners have done this with no ill effects except the occasional keys left in the ignition and flights out of the car when they didn't buckle up! In other words, it's more likely to damage you than your car. Disconnecting this module shouldn't affect the functionality of most alarm systems, but it's possible that it could. Disconnecting the buzzer does not stop the airbag alert from working.

I've always disconnected the buzzer modules in every car I've owned and never had a problem. I've heard of Miatas with their buzzers disconnected for many years with no problems. I did this mod first on both my '94C and '03LS with no (noticable) problems.

The only thing that could damage the car is if you don't properly insulate the wires you have removed. Many of them have +12V running through them and could contact the frame and blow a fuse. This could also, potentially, set the car on fire. You should wrap them in electrical tape or heat-shrink tubing and tuck them out of the way!

Q) What's this about the airbag alert?

A) Disconnecting the buzzer module does not affect the secondary airbag alert feature! There is a separate buzzer in the airbag computer for this function.

Q) What other creative ways can I use this buzzer?

A) People on the miata mailing list have used this buzzer for a headlights-on warning, or "light minder", among other things. Search the miata mailing list archives for the following messages for their messages or read on!

  • Mario Amato, January 1995, "Subject: Headlight reminder from key buzzer"
  • Greg Edgar, January 1996, "Subject: Better Light Minder"
  • Greg Edgar, January 1996, "Subject: RE: Better Light Minder"
  • Henry C. Barta, January 1998, "Subject: key minder buzzer to light minder buzzer"

Q) How do I convert this buzzer into a "light minder"?

A) There is a commercial product called a "Lite Minder" which is sold at many Miata specialty stores and discount chains. It sounds a buzzer when you leave the lights on and open the door. Many automobiles include this feature from the factory as well. In fact, my '03LS has this function built in. Good thing, too, because I don't think this mod will work on an M2! Anyone tried it?

Some people on the Miata mailing list got the bright idea of turning the Key Minder buzzer into a light minder. Others have ridiculed this idea, noting that the "barn doors" and the lights themselves should be enough of a reminder. However, since many Miata owners use parking lights (or driving lights) on cloudy days to improve visibility, such a buzzer might prove helpful.

This modification, as described, requires no cutting. For surer connections, either use a t-connector or cut and solder the wires in place. Be sure to insulate all exposed wires with electrical tape or heat-shrink tubing or you will be sorry when your car bursts into flames!

To turn your Key Minder into a light minder, just follow these simple instructions:

  1. Get a large phillips-head screwdriver and a piece of 18-gauge (or similar) insulated wire. Strip off a bit of insulation at the ends to expose the wire.
  2. Optionally get a diode (just about any one should do) and attach this in the middle of the wire. When installing the wire, make sure the band mark is on the buzzer side, not the ignition side.
  3. Put the key in the ignition.
  4. Open the door. Hear the buzzer? Good.
  5. Unscrew the flat metal panel under the steering wheel and pull it out of the way.
  6. Locate the connector near the ignition switch. On cars with manual transmissions, this will be a two-wire connector with one blue/yellow wire and one blue/red wire. On cars with automatics, this will be a four-wire connector with blue/red, white/green, blue/white, and blue/yellow wires. The blue and yellow striped wire is the important one!
  7. Unplug the connector. The buzzing should stop. If not, plug it back in and go fishing again!
  8. Take the key out of the ignition and optionally disconnect the car battery for safety.
  9. Use a or flat screwdriver to pry the dimmer switch from the dash panel. Pull it out until you can get at the wiring connector on the back of it. Boy it sure is a long switch!
  10. Unplug the connector from the back of the dimmer and hold the connector with the switch side facing you. The pinout of this switch is as follows:
    Output Ground
    NC Input NC NC
    Red wire. This is the output of the dimmer switch and goes to the interior lights.
    Black wire. This wire is continuous to ground.
    Red/black striped wire. This is input power provided by the light switch on the stalk. It should be 10 to 12 volts.
    These are not connected.
  11. Make sure the lights are off so this wire won't be live. Carefully shove one end of your new wire into the dimmer connector along with the red/black wire. Make sure it's snug and that no wire is exposed outside the connector! Tape the wire to the existing red/black wire with electrical tape to keep it in place.
  12. Run your new wire back through the hole, through the metal hole that leads to the steering column and around to the connector you unplugged before. Tape or fasten it in places so it won't rattle around.
  13. Once again, carefully shove the wire end into the connector with the blue and yellow striped wire and fasten it into place with electrical tape. If you have a added a diode to your wire, you can leave this plugged in to have both a key minder and a light minder. Otherwise, you must leave it unplugged! Note that leaving this connector unplugged on cars with automatic transmissions will have unknown consequences, so automatic owners should always use the diode method and leave this plugged in!
  14. Secure all wires in place with cable ties, twist-ties, or electrical tape. Then plug the connector back into the dimmer switch and replace it in its socket in the dash. Screw the steering column plate back into place as well.
  15. You should now have a working light minder buzzer! Test it by turning on the lights and opening the door while the car is off. Start the car and it should shut up. Does it work? If not, go back and re-check the connections. If you can't get a good connection, you may have to cut and solder the wires or at least use T-connectors and spade lugs.

You can use a slight modification of this approach to have a whatever-minder! Many people use it as a fog-light minder, but anything with a 10-12 volt power supply can be used to trigger the buzzer. Add a few diodes and the same buzzer can alert you to many things! Please let me know if you think of other creative uses for the buzzer and I'll add them here!

Thanks to Hank Barta, Mario Amato, Greg Edgar, and Jeff Anderson for this information!

Q) You don't know what you're talking about with this stuff.
How can I set you straight?

A) PLEASE contribute! If you have any more info on any of this stuff, send it along! My email address is

Also, please note that all of this information applies to the US Miatas, but some may not be correct for the Miatas in other countries.

Thanks for info in this FAQ to: Will Brown, Lanny Chambers, Jeff Anderson, Hank Barta, Mario Amato, Lance Schall, and Greg Edgar