The Throttle Position Sensor (TPS) is mounted to the side of the throttle body and connects to the throttle blade shaft. The TPS is a variable resistor that provides the PCM with an input signal (voltage). The signal represents throttle blade position. As the position of the throttle blade changes, the resistance of the TPS changes.
The PCM supplies about 5 volts of DC current to the TPS. The TPS output voltage (input signal to the PCM) represents throttle blade position. For 1995 vehicles, the TPS output voltage to the PCM varies from about 0.5 volt at idle to a maximum of 3.7 volts at wide open throttle. For 1996-98 vehicles, the TPS output voltage to the PCM varies from about 0.35-1.03 volts at idle to a maximum of 3.1-4.0 volts at wide open throttle.
Along with inputs from other sensors, the PCM uses the TPS input to determine current engine operating conditions. The PCM also adjusts fuel injector pulse width and ignition timing based on these inputs.
See Figures 1, 2 and 3
In order to perform a complete test of the TPS and related circuits, you must use a DRB® or equivalent scan tool, and follow the manufacturer's directions. To check the Throttle Position Sensor (TPS) only, proceed with the following tests.
Visually check the connector, making sure it is attached properly and that all of the terminals are straight, tight and free of corrosion.
- The TPS can be tested using a digital ohmmeter. The center terminal of the sensor supplies the output voltage.
- Connect the DVOM between the center terminal and sensor ground.
- With the ignition key to the ON position and the engine OFF check the output voltage at the center terminal wire of the connector.
Check the output voltage at idle and at Wide Open Throttle (WOT):
For 1995 vehicles at idle, the TPS output voltage should be about 0.5 volts. At WOT, the output voltage should be about 3.7 volts. The output voltage should gradually increase as the throttle plate moves slowly from idle to WOT.
Check the resistance of the TPS as follows:
- Unplug the TPS connector.
- Using an ohmmeter, or a DVOM set to the ohms scale, measure the resistance between terminals 1 and 3 of the connector on the TPS side.
- Resistance should measure 3.5-6.5K ohms.
- Measure the resistance between terminals 2 and 3 of the connector on the TPS side.
- Measure the resistance with the throttle closed, with the throttle about halfway open and at wide open throttle.
- The resistance should increase smoothly as the throttle plate is opened.
- If resistance measures outside these values, replace the TPS.
- Before replacing the TPS, check for spread terminals and also inspect the PCM connections.
REMOVAL & INSTALLATION
See Figures 4, 5 and 6
- Disconnect the negative battery cable.
- Disconnect the EVAP purge hose from the throttle body.
- Detach the electrical connector from the IAC motor and the TPS.
- Remove the throttle body from the vehicle, as outlined in Fuel System of this repair guide.
- Unfasten the mounting screws, then remove the TPS from the throttle body.
- The throttle shaft end of the throttle body slides into a socket in the TPS. The socket has 2 tabs inside it. The throttle shaft rests against the tabs. When indexed correctly, the TPS can rotate clockwise a few degrees to line up the mounting screw holes with the screw holes in the throttle body. The TPS has slight tension when rotated into position. If it is difficult to rotate the TPS into position, install the sensor with the throttle shaft on the other side of the tabs in the socket.
- Install the sensor mounting screws and tighten to 17 inch lbs. (2 Nm).
- After installing the TPS, the throttle plate should be closed. If the throttle plate is open, install the sensor on the other side of the tabs in the socket.
- Install the throttle body, as outlined in Fuel System .
- Attach the electrical connectors to the IAC motor and TPS.
- Connect the EVAP purge hose to the throttle body nipple.
- Connect the negative battery cable.