Transfer gearbox – circuit operation

TRANSFER GEARBOX – CIRCUIT OPERATION

Neutral Switch (X308) or Clutch Switch-
pin 34 A shift between ranges is possible when the transmission is in neutral. The Transmission Gearbox Control Unit (Z256) senses this via a Park/Neutral Switch (X308) on automatic transmission vehicles and via either a clutch switch or a lever neutral switch on manual transmission vehicles. This signal is passed via the BeCM (Z238).

Interface to “H-Gate”-
pin 35, 15 (automatic

transmission only)

The H-Gate gets the range information via a High and Low status signal from the output of the Transmission Gearbox Control Unit (Z256); e.g. when the vehicle is in High then the High side of the “H” is illuminated. When a range change to Low is requested, the Low side of the “H” starts to flash whilst the High side stays constant. When Low range is obtained then the flashing light on the Low side changes to constant and the High side light goes off. If a range change is requested and not all of the conditions are satisfied, then the current range will stay illuminated and the desired range will flash and continue flashing until all of the parameters are satisfied or the request is removed. If the gear lever is placed in the neutral position for the gearbox and the transfer box then, after a five second safety delay, the transfer box moves to neutral and the lights on both side of the “H” are extinguished.

Interface to Auto Gear Box Control Unit (Z255) - pin 35

The High/Low signal to the Auto Gear Box Control Unit (Z255) comes from the High range status lamp. If the Auto Gear Box Control Unit (Z255) does not receive the range information, then an incorrect gear change mode could be selected, i.e. Manual rather than Sport in High range and vice versa in Low range. Also, the shift strategy is different between the Economy modes of High and Low and so poor shift quality could result.

Automatic Selector Park Interlock

When the gear selector lever is in the park position, the shift interlock solenoid is deenergized and prevents the selector from being moved to another gear. To free the selector, the Ignition Switch (X134) must be in position II and the brake pedal must be depressed.

Current is then supplied to the solenoid through the PR wire via fuse 13. The solenoid is grounded using the B wire to the console ground E621. The solenoid is now energised, freeing the selector. The solenoid is energised continuously whilst the selector lever is in any position other than park and the Ignition Switch (X134) is in position II.