Throttle Position (TP) Sensor - (From 99MY)

The TP sensor is located on the rear of the throttle body assembly in the engine compartment and fixed to its mounting studs by two screws.

The TP sensor is a potentiometer having a resistance track that is connected to a stabilized 5V supply at one end of its track and ground at the other end of the track. The potentiometer wiper arm is connected to the throttle plate assembly and provides a signal to the ECM which is an analogue voltage between 0.162mV (closed throttle) and 0.811mV (wide open throttle), corresponding to the throttle valve angle. The TP sensor connector terminals are gold plated for good conductivity and corrosion resistance; care should be exercised if it is necessary to probe the connector and sensor terminals.

The TP sensor enables the ECM to determine the throttle valve's position and angular velocity. The ECM uses the data from the throttle valve position for determining intake-air volume, which it uses for calculating the necessary fuel injection duration under various operating conditions. The data from the throttle valve's angular velocity is used mainly for acceleration/deceleration compensation. The ECM also uses closed throttle position for idle speed control in conjunction with road speed.

The TP sensor also supplies the ECM with information to enable the overrun fuel shut off strategy to be implemented. When the ECM receives closed throttle information from the TP sensor, it closes the injectors for the duration of the closed throttle time.

A software strategy within the ECM enables the closed throttle position to be learned, so that the sensor can be fitted without the need for adjustment.

The throttle position signal is also supplied to the EAT ECU from the ECM using the CAN communication link. The EAT ECU uses the throttle position data to determine the correct point for gear shifts and acceleration kickdown.

If the TP sensor signal fails, the ECM uses a default value derived from engine load and speed. A TP sensor failure may result in the following symptoms being experienced:
- Poor throttle response and degraded engine performance
- Emission control failure.
- Closed loop idle speed control inoperative.
- Automatic gearbox kickdown inoperative.
- Incorrect altitude adoption
- MIL illuminated (NAS only)

A TP sensor failure is likely to occur for the following reasons:
- Sensor open circuit
- Short circuit of signal line to vehicle supply, 5V supply or ground.
- Bad connection or increased resistance in wiring harness causing signal offset.
- Blocked air filter (load monitoring, ratio of the TP sensor to air flow).
- Restricted air inlet (load monitoring, ratio of the TP sensor to air flow).

If the TP sensor should fail, the following fault codes will be generated by the ECM diagnostics, which can be retrieved by Testbook:

- P0101 - (load monitoring, the ratio of throttle position to air flow).
- P0122 - (signal less than the minimum threshold).
- P0123 - (signal greater than the maximum threshold).