Note: The throttle position sensor is fitted to XL600V-T to X (1997 to 1999) models, XL650V models, and XRV750-T models onwards (1996-on).
Check
1. The throttle position sensor (TPS) is mounted on Hie right-hand side of the front cylinder carburettor and is keyed to the throttle shaft. The sensor provides the ignition control unit with information on throttle position and rate of opening or closing.
2. Remove the fuel tank (see Chapter 4). Disconnect the sensor's wiring connector (see illustration 7.6a in Chapter 4).
3. Connect the probes of an ohmmeter between the green/black and yellow/black terminals on the sensor and measure the resistance. Compare the reading to the value specified at the beginning of the Chapter.
4. Now connect the probes between the yellow/black and red/yellow terminals on the sensor. Slowly open the throttle from fully closed to fully open and back to fully closed. Check that the resistance Increases as the throttle is opened and decreases as it is closed.
5. To check the input voltage to the sensor, connect the positive (+) lead of a voltmeter to the green/black wire terminal on the connector and the negative (-) lead to the yellow/black wire terminal. Turn the ignition switch ON and check that a voltage of 4.7 to 5.3 volts is present. If it isn't, there is a fault in the wiring or the ignition control unit.
6. If the throttle position sensor functions correctly then the fault must be in the wiring harness or the ignition control unit (ICU). Check the wiring between the TPS connector and the ICU connector for continuity, and check the connectors themselves for loose or broken terminals. If the wiring is good the ICU could be faulty (see Section 5).
Replacement
Note: The sensor is not available separately from the carburettor bodies on XL600 and 650 models, and is only available as a unit with its mounting bracket on XRV750 models. Do not disturb it unnecessarily.
7. Remove the carburettors (see Chapter 4). The throttle sensor is mounted on the righthand end of the carburettor assembly (see illustration).

7.7. Throttle position sensor (arrowed)
8. Undo the three screws which retain the sensor mounting bracket to the carburettor body - do not disturb the screws which secure the sensor to its bracket.
9. Install the sensor, locating the tab on the throttle shaft in the cutouts on the inside of the sensor, and tighten the screws securely.