The throttle position sensor, mounted to the throttle body assembly, is a potentiometer type sender which provides a signal to the electronic control module that is related to the relative throttle plate position. As the throttle plate moves in relation to driving conditions, a signal is sent to the control unit which adjusts the injector pulse width and air/fuel ratio. As the throttle plate is opened further, more air is taken into the combustion chambers, and as a result the relative fuel demand of the engine changes. The throttle position sensor relays this information to the control unit which in alters the fuel amount.
See Figure 1
- Visually inspect the throttle linkage and throttle for binding and sticking.
- With the key in the ON position, use a multimeter and test for voltage at the two outside wires of the harness. Voltage should be between 4-6 volts. If there is no voltage present, check the wire harness for a break, or the fuse box for a blown fuse.
- Connect a breakout box between the powertrain control module and the powertrain control module wire harness.
- Start the engine and allow to reach normal operating temperature. Record the voltage between the signal and return terminals at the breakout box while slowly opening the throttle plate. Depending on the throttle plate position, the voltage will be between 0.17-0.49 volts. If the voltage level is below or above the specified amount, replace the switch.
REMOVAL & INSTALLATION
See Figures 2 and 3
When the battery cable has been disconnected and reconnected, some abnormal drive symptoms may occur while the powertrain control module relearns its adaptive strategy. The vehicle may need to be driven 10 miles (16 km) or more to relearn the adaptive strategy.
- Disconnect the negative battery cable.
- Unfasten the throttle position sensor electrical connector from the side of the throttle body assembly.
- Scribe alignment marks on the throttle body and TPS sensor to indicate proper alignment during installation.
- Remove the screws retaining the TPS electrical connector to the air throttle body.
- Remove the TPS and gasket from the throttle body. Remove any gasket material from the mating surfaces.
- If installing a new TPS switch, compare the replacement sensor with the original, then scribe an alignment mark on the new sensor in the same area as the old one for proper alignment.
- Place the TPS and new gasket on the throttle body, making sure the rotary tangs on the sensor are aligned with the throttle shaft blade. Slide the rotary tangs into position over the throttle shaft blade, then rotate the throttle position sensor CLOCKWISE ONLY to the alignment marks made earlier.
- Once the scribe marks are aligned, install the TPS retaining screws and tighten them to 11-16 inch lbs. (14-21 Nm).
- Fasten the TPS electrical connector.
- Connect the negative battery cable.
- Start the engine, and check the idle speed. If installed correctly, the idle speed should be within specification.
Adjustment of the throttle position sensor requires the use of expensive test equipment that is not available to the do-it-yourself market. If adjustment is required, it should be performed by a qualified technician with the proper training and equipment to diagnose and repair the EEC-IV engine control system.