Automatic gearbox – circuit operation

AUTOMATIC GEARBOX – CIRCUIT OPERATION

MV2 is also used to prevent the driver from selecting reverse when the vehicle is moving forward at more than 8 km/h and from disengaging reverse at reverse speeds greater than 6 km/h. This is known as “Reverse Safety” and will not be available if MV2 is non-operational and/or the gearbox has defaulted. Torque Converter Lock-Up Solenoid - pin 42: The torque converter slips to allow smooth operation of the gearbox. Lock-Up occurs when the vehicle reaches a speed of 45MPH or above in either third or fourth gears. Pressure Regulator Solenoid - pin 6: The gear shift quality is controlled by modulating the pressure regulator, which is controlled by the Auto Gear Box Control Unit (Z255). The solenoid is energised closed, such that if a failure occurs, then the regulator allows default gear change.

Output Shaft Speed Sensor -pins 2, 38, 20

The automatic gearbox system incorporates an output shaft speed sensor which is input to the Auto Gear Box Control Unit (Z255) on pins 2 and 38 with a screen over the cable attached to pin 20. It is important that this signal is screened correctly.

MES 1 and 2-pins 16, 31

The two Manual/Economy/Sport (MES) lines indicate to the BeCM (Z238) which mode has been selected or if a fault within the transmission has occured.

Interface to Transmission Gearbox Control Unit (Z256) -High/Low Range Signal-pin 46

The High/Low signal is used by the Auto Gear Box Control Unit (Z255) to select the correct mode on application of the “MES” switch. Also, the gear shift points and strategies are very different in the different ranges.

Interface to “H-Gate”-pin 29

The “H”-Gate sensor module (Z254) displays selected gear information from the Gear Box Position Switch (X294), ratio information from the Transmission Gearbox Control Unit (Z256) and mode information from the gear box Auto Gear Box Control Unit (Z255). The H-Gate receives an ignition 2 signal on the W wire. This is fed via fuse 6. It is grounded to the console ground E621 via the B wire. Information on the selected gear (PRNDL) is received from the Gear Box Position Switch (X294) on wires UB, UP, UG. These three lines also go to

the Auto Gear Box Control Unit (Z255) and the BeCM (Z238). Information on the gear box mode (sport or manual) is received on the YG wire and the YR wire. These two lines also go to the BeCM (Z238). The Transmission Gearbox Control Unit (Z256) high status is received on the NY wire. The low status is received on the NR wire. These two lines also go the Transmission Gearbox Control Unit (Z256) and the BeCM (Z238). The illumination signal is on the RU wire. The mode request is on the UO wire. This is sent from the H-gate Sensor Module (Z254) to the Auto Gear Box Control Unit (Z255). The line is activated and deactivated by pressing the momentary action MODE button. The line is active at all times.