Electric Throttle
The electric throttle is located between the charge air cooler connecting pipe and the intake manifold. The electric throttle is secured to the manifold with 4 bolts.
The electric throttle comprises the throttle body, a round throttle butterfly valve. The butterfly valve is actuated by a Direct Current (DC) motor. The electric throttle also comprises the Throttle Position Sensor (TPS). The electric throttle is controlled by the Powertrain Control Module (PCM) which receives positional signals from the TPS.
If a failure of the motor occurs, the butterfly valve is returned to an emergency position by springs. The butterfly valve remains partially open with limited engine speed available to the driver.
The electric throttle has 5 wires which are connected to the PCM:
- The DC motor is supplied with 12V and ground on 2 wires.
- A wire supplies a reference voltage to an analogue, Hall effect sensor in the TPS.
- The 2 further wires provide the TPS negative and positive signal feedback to the PCM.
As the throttle angle increases, the output of the negative sensor decreases and the output of the positive sensor increases.
The motor is a DC motor which drives a gear wheel and two springs, one for opening and one for closing. The motor rotates the spindle to which the butterfly valve is attached. The PCM uses Pulse Width Modulation (PWM) signal to adjust the position of the butterfly valve. The amount of air entering the inlet manifold is regulated by the position of the butterfly valve. Movement of the motor is achieved by changing the polarity of the power supply to the DC motor, allowing it to be operated in both directions.
The butterfly valve and the DC motor has two maximum positions:
- Butterfly valve closed which allows minimal air flow through the electric throttle into the intake manifold.
- Butterfly valve open which allows maximum air flow into the intake manifold.
The PCM calculates the butterfly valve position by comparing the feedback signal from the TPS. The PCM does a self-test and a calibration routine on the butterfly valve position at each ignition cycle. This is achieved by the PCM powering the DC motor to fully close the butterfly valve and if required, fully open the butterfly valve.
The PCM monitors the DC motor and the TPS for faults and can store fault related Diagnostic Trouble Code (DTC). The DTCs can be retrieved using the Jaguar Land Rover (JLR) approved diagnostic equipment. In the event of a fault the engine Malfunction Indicator Lamp (MIL) is also illuminates in the Instrument Cluster (IC).