Automatic gearbox - Jatco (1): Description and operation (page 2 of 4)

Intermediate Speed Sensor

The intermediate speed sensor is located within the gearbox. The EAT ECU uses this sensor to ensure correct gear engagement and to monitor the amount of slip within the gearbox.

The EAT ECU calculates the slip within the gearbox by comparing the difference between the inputs from the intermediate speed sensor and the turbine speed sensor.

The intermediate speed sensor detects the output gear rotation speed and sends an electrical output to pin 51 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 54 pulses per revolution of the output gear.

The intermediate speed sensor can fail in the following ways: l Sensor open circuit l Short circuit to 5 or 12 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 sensor output is equivalent to less than 600 rev/min for two seconds.

In the event of an intermediate 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.