Electronic Transmission Control Introduction 1-10-03.qxd - GE39

AC Compressor Load Sensing (Hydramatic Transmissions)
When the AC Compressor is switched on, additional load is placed on the engine. To compensate
for the additional load, the TCM modifies line pressure and shift points. On the
THMR-1, the TCM receives these signals via a direct connection to the AC compressor
control circuit.
On vehicles equipped with CAN bus technology, the “AC on” signal is sent to the TCM from
the DME as a CAN bus message.
Shift Lock
The shift lock solenoid is mounted on the
selector lever assembly and locks the selector
lever in Park or Neutral when the ignition is ON.
This prevent the selection of a gear unless the
brake pedal is depressed. The solenoid is activated
by a switched ground from the TCM.
Power is supplied by the TCM internal relay.
During failsafe operation, the shift lock is disabled.
On later models, the shift lock will also
be active when the TD signal is present and the
shifter will remain locked above an engine
speed of 2500 RPM regardless of brake application.
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Electronic Transmission Control