Automatic gearbox - Jatco (1): Description and operation (page 3 of 4)

Turbine Speed Sensor

The turbine speed sensor is located within the gearbox and is used by the EAT ECU to monitor the input shaft speed. The EAT ECU uses this sensor to ensure the correct gear ratio is selected and to ensure that there is not excessive slip within the gearbox drive train.

The turbine speed sensor detects the input shaft speed (turbine speed) and sends an electrical output to pin 24 of the EAT ECU which also supplies an earth path for the sensor on ECU pin 20.

The sensor is an inductive sensor that produces a sinusoidal output at a frequency of 36 pulses per revolution of the input shaft.

The turbine speed sensor can fail in the following ways: l Sensor open circuit l Short circuit to 12 or 5 volts l Short circuit to earth.

The EAT ECU will detect sensor failure if the vehicle speed exceeds 25 mph (40 km/h) and the engine speed is above 1300 rev/min, but the turbine speed is below 600 rev/min for two seconds.

In the event of a turbine speed sensor signal failure any of the following symptoms may be observed: l Upshift to 5th gear inoperative l Torque reduction request from the EAT ECU to the ECM inoperative.

A failure of the sensor will generate a 'P' code which can be retrieved using TestBook/T4 or any Keyword 2000 diagnostic tool.