Throttle Position Sensor

The throttle position sensor on the 1990-1993 Miata is about the strangest setup I’ve ever seen before. Its not a normally tps sensor at all. It basically only has 3 states. Idle, not idle and wide open throttle. That’s it. There is no gradual change like in a normal tps setup.

So here’s the notes I’ve found on it so far :

The TPS is a single-pole, double-throw switch with center “off” position, and works like this:

1) The “TL” terminal of the TPS (wiper of switch) is connected to ground through the TPS connector’s wire harness.

2) The “POW” terminal (WOT terminal of switch) is supplied with +5 volts from terminal 2L of the ECU, when ignition is ON.

3) The “IDL” (“idle” terminal of switch) is supplied with +12 volts from terminal 1N of the ECU, when ignition is ON.

When the TPS is between “idle” and WOT, the wiper of the TPS switch is not contacting either of the other two terminals of the TPS, so ECU terminal 2L will be at +5 volts, and ECU terminal 1N will be at +12 volts.

When TPS is in “idle” position, its wiper grounds ECU terminal 1N, and ECU terminal 2L will be at +5 volts.

When TPS is at WOT, its wiper grounds ECU terminal 2L, and terminal 1N will be at +12 volts.

The three modes determine the appropriate ECU responses.

Note: The “POW” terminal is the top terminal, the “TL” terminal is the middle one, and the “IDL” terminal is the bottom one.

The adjustment is made by loosening the mounting screws and rotating the TPS cover to get the following conditions:

1) In the idle position, slide a 0.016″ feeler gauge between the throttle adjust screw and the throttle butterfly flange. For that condition, there should be electrical continuity between the middle and bottom terminals of the TPS electrical connector.

2) Now change the feeler gauge thickness to 0.027″ and there should be no continuity among any of the three terminals. Then re-tighten the mounting screws and recheck.

3) After setting the rotation to meet the above requirements, check to make sure that if the accelerator pedal is at wide open throttle position, there is continuity between the top and middle TPS connector terminals.

Testing the 1.6 TPS

From the top to the bottom, the terminal names are:

POW – Indicates Wide Open Throttle
TL – Common
IDL – Indicates Throttle Closed

This is a double pole single double throw switch with the center off.

The common terminal is TL.

With the wiring harness disconnected and the TPS still in place on the throttle body, using an ohmmeter:

With the throttle at rest (and properly adjusted), there will be continuity between TL and IDL.
With the throttle at maximum, there will be continuity between TL and POW.

Adjusting the 1.6 TPS

Using an Ohm meter, measure for continuity between terminals TL and IDL:

With a .016 inch feeler gauge inserted at the throttle stop screw, you should have continuity.
With a .027 feeler gauge inserted, no continuity.

If adjustment is needed, loosen the TPS screws and rotate the sensor to achieve these results.


For a replacement pigtail connector for your tps harness


Standard Motor Products

Throttle Position Sensor Connector

Part Number: 8532-05228211

So just go to and enter the above part number. Was $12.98 as of this article.


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