Vanden Plas (X308) V8-4.0L (AJ27) (2000)
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Transmission Speed Sensor: Description and Operation
Transmission Speed Sensors (Gear Shift Control)
Operation
There are two speed sensors within the transmission assembly; one on the input shaft or convertor turbine and the other on the output shaft.
Both sensors are of the inductive type and sense toothed wheels; the input wheel having 30 teeth and the output 36 teeth.
Input speed is monitored by the TCM with a rationality check being made against output speed. A fault will be flagged if the indicated input speed
exceeds 7400 rpm. Additionally, a failure judgement will be made if the indicated input speed is <160 rpm with engine speed >608 rpm and output
speed >224 rpm
The procedure is similar for the output speed diagnostic. A fault (non OBDII) will be flagged if the indicated input speed exceeds 6712 rpm.
Additionally a failure judgement will be made if the indicated output speed is <160 rpm and the average road wheel speed exceeds 100 rpm.
Under normal circumstances after the output speed diagnostic fault code has been set, the TCM uses rear wheel speed information to compute its
calculations, this has no effect on transmission operation. However, should a second fault occur, in the ABS system, thus making rear wheel speed
information unavailable, an additional fault code will be logged.
