Starting System: Description and Operation

Inhibitor Switch

Description

The inhibitor switch is located externally on the right hand side of the transmission. The switch is located on the selector shaft and secured to the main casing with screws. A protective cover is also fitted over the switch to prevent impact damage. The switch rotates with the selector shaft, moving the switch contacts to correspond to the selected programme.

The switch provides signals that allow the TCM to monitor the position of the manual selector spool valve and the selected drive programme. The switch is connected via an integral harness and multiplug on five wires to the TCM. One of the wires supplies a 12 V supply to the switch. The remaining wires are connected to the TCM. When the transmission selector lever is moved to the selected position, one or more of the contacts within the switch are made, completing a circuit back to the TCM. From the switch contacts that are made, the TCM determines which selection is required and responds accordingly.

There are two diagnostic checks of the Inhibitor switch, an error is detected if:-
1. The ignition supply is greater than 9 V and an incorrect position code has been received.
2. The ignition supply is greater than 9 V the engine is cranking and the position code does not indicate a park or neutral state.