Jeep Wagoneer/Commando/Cherokee 1984-1998

Throttle Position Sensor



The Throttle Position Sensor (TPS) is located inside the carburetor. It is a potentiometer with one wire connected to 5 volts from the ECU and the other to ground. A third wire is connected to the ECU to measure the voltage from the TPS.

As the accelerator pedal is moved, the output of the TPS also changes. At a closed throttle position, the output of the TPS is low (approximately 0.5 volts). As the throttle valve opens, the output increases so that, at wide-open throttle, the output voltage should be approximately 4.5 volts.

By monitoring the output voltage from the TPS, the ECU can determine fuel delivery based on throttle valve angle (driver demand).

Removal & Installation

  1. Remove the upper and lower bonnet assemblies.
  3. Remove the throttle body assembly from the vehicle.
  5. Remove the two Torx® head retaining screws holding the TPS assembly to the throttle body.
  7. Remove the throttle position sensor from the throttle shaft lever.
  9. Installation is the reverse of removal. Adjust the sensor.

Make sure that the sensor arm is installed UNDERNEATH the arm of the throttle valve shaft!


See Figure 1

A tamper-resistant plug covers the TPS adjustment screw. This plug should not be removed unless diagnosis indicates the TPS sensor is not adjusted properly or it is necessary to replace the air horn assembly, float bowl, TPS sensor or TPS adjustment screw. This is a critical adjustment that must be performed accurately and carefully to ensure proper engine performance and emission control. If TPS adjustment is indicated, proceed as follows:

  1. Use a 5 / 64 in. (2mm) drill bit to drill a hole in the steel cup plug covering the TPS adjustment screw. Use care in drilling to prevent damage to the adjustment screw head.
  3. Use a small slide hammer to remove the steel plug from the air horn.
  5. Unplug the TPS connector and use jumper wires to connect all three terminals.
  7. Connect a digital voltmeter between the TPS connector center terminal B and the bottom terminal C (ground).
  9. With the ignition ON (engine OFF ), turn the TPS adjustment screw to obtain 0.26 volts (260 mv) at the curb idle throttle position with the A/C off.
  11. After all adjustments are complete, a new tamper-proof plug (supplied in service kits) or silicone RTV rubber sealant must be inserted into the TPS adjustment screw hole to seal the adjustment. If a plug is used, it should be installed with the cup facing outward and flush with the top of the casting.

Click image to see an enlarged view

Fig. Fig. 1: TPS adjustment. (1) is the adjustment screw plug; (2) is the adjustment screw; (3) how to connect jumper wires