1-13
Operation Pride
Interface with Body electronic Control Module (BeCM) , see schematic 1
The BeCM provides power to the TCM via an ignition feed fuse F6 and a permanent feed via fuse F3.
In addition to power, the BeCM also routes the engine speed signal that the GEMS ECM outputs
and the diagnostic K/L lines that go to the Data Link Connector (DLC). The TCM, ECM, HEVAC,
ABS and BeCM are all attached to the same K/L lines in the DLC.
The TCM also uses the Manual Economy Sport (MES) lines to signal to the BeCM what mode of
operation it is in. If a fault condition occurs, these lines will remain high (battery voltage minus 2
volts) to indicate to the BeCM that the TCM has encountered some form of failure. The BeCM
uses this information to send a “GEARBOX FAULT” message to the instrument pack message
center.
The BeCM also receives the gear position switch information to allow it to display the currently se-
lected gear on the message center. However, it too does not need the reverse selection or starter
inhibit switch positions as it can determine this information from the status of the “XYZ” switches.
The MES lines are also connected to the H-Gate so that the currently selected gear can be indi-
cated by a “red dot” on the shifter mechanism.
Interface with the Transfer Box Control Unit (TCU) , see schematic 1
The High/Low signal is used by the TCU to select the correct mode on application of the “MES” switch
lines, i.e. Economy or Sport modes in High range and Economy or Manual modes in Low range.
Shift points are very different in the Economy mode in the High/Low ranges. In addition, it should
also be noted that cruise control does not function when in low range. Cruise control is controlled
by the BeCM and not the TCM.
Solenoid Valves
The TCM has control over four solenoid valves: MV1 (shift valve 1), MV2 (shift valve 2), pressure
regulator and torque converter lock up.
The power for all the solenoids comes from the TCM via pin 19; this power is controlled by an in-
ternal relay. If any fault occurs which needs limp home capability, the TCM will interrupt the power
supply. Interupting the power supply defaults the transmission to third if the vehicle was stationary
and fourth if the vehicle was moving. Figure 1 shows the transmission electrical connections and
the resistance across all pins. The transmission electrical connector is located on the left hand
side of the transmission about 8 inches from the rear of the gear position switches.
Shift Valves
When the driver selects Drive, the TCM controls the gear selection by the use of the two solenoid
valves, MV1 and MV2. If a fault occurs in one or both of these valves, then a different gear than
the one selected will result. If the TCM defaults the transmission, then the common supply to all
the solenoid valves is removed and the transmission mechanically shifts either to third gear, if the
vehicle is stationary, or fourth, if moving. MV2 is also used to prevent the driver from selecting re-
verse when the vehicle is moving at more than 8 km/h ( 5 mph) and from disengaging at reverse
speeds greater than 6 km/h (4 mph). This is known as “Reverse Safety” and will not be available if
MV2 is non-operational or the transmission is defaulted. Figure 1 shows the transmission electri-
cal connections and the resistance across all pins.