Shift interlock (where fitted)
On automatic gearbox models, the BCU and IDM combine to operate a shift interlock solenoid, so that the gear selector lever can only be moved when certain logical conditions have been satisfied. Operation of the interlock may be affected, if the battery becomes discharged.
When the gear selector lever is in the Park position and the ignition is off, an interlock solenoid is de-energized, locking the gear selector lever in the Park position.
The gear selector lever can only be moved from the Park position when the ignition is switched on and the brake pedal is depressed. When these conditions are satisfied, the brake pedal switch signal is received by the BCU which then signals the IDM to energize the interlock relay. When the interlock relay is energized, the interlock solenoid is operated, unlocking the gear selector lever.
When the brake pedal is released, the feed to the BCU is removed and the shift interlock solenoid is de-energized. The locking mechanism controlled by the solenoid will lock the gear selector lever once it is returned to the Park position.
The shift interlock option can be programmed in one of three states dependent on market/ customer requirements, these are:
- Option 1- not fitted.
- Option 2 - normal operation.
- Option 3 - inhibit transfer box.
The BCU checks the status of the following inputs to determine the logic action for employing the shift interlock solenoid:
- Brake switch activated.
- Ignition state.
- Gearbox state.
In the event of a communications link failure, the shift interlock solenoid enable is switched on for 1 minute every time the ignition is switched on and switched off when the ignition is turned off.