Engine Sensor Inputs; Torque Converter - Hummer H1 Service Manual

_____________________________________________
Transmission/Transfer Case 5-9
®

ENGINE SENSOR INPUTS

PRESSURE
The electronic accelerator pedal, coolant temperature sensor,
REGULATOR
A/C switch, brake switch, and crankshaft position sensor, all
VALVE
affect transmission operation.
The electronic accelerator pedal input signals inform the PCM
of throttle position. This input affects pressure control solenoid
operation and transmission line pressure. The solenoid in-
creases line pressure at higher throttle openings.
The coolant temperature sensor input affects transmission
shifting. The sensor signal can prevent shifts into overdrive
fourth gear when coolant temperatures are low or extremely
high.
Crankshaft position sensor inputs are used by the PCM to ad-
just shift points and fluid pressures.
A signal from the A/C switch informs the PCM when the A/C
switch and compressor are engaged. This signal affects trans-
REVERSE/
mission shift points to compensate for increased engine load
BOOST
and idle rpm.
VALVE
The brake switch signal is used by the PCM to control down-
EXHAUST
shift points and torque converter release. Brake application
PORT
completes the switch circuit to the PCM which then downshifts
the transmission as needed.

TORQUE CONVERTER

The torque converter consists of a cover, clutch pressure plate
and damper, turbine, stator, and pump (Figure 5-14).
A roller clutch in the stator hub prevents stator freewheeling
Figure 5-13: Pressure Control Solenoid Boost
until coupling speed is reached. The clutch maintains torque
Schematics
multiplication until this point.
The converter clutch, located between the cover/impeller and
the stator, eliminates normal internal slippage at cruise speeds.
The clutch pressure plate has friction material bonded to it that
engages the cover/impeller when applied. Clutch applied at
normal cruise speeds improves fuel economy and reduces fluid
temperature.
The converter is not a repairable part. It is serviced only by re-
placement.
05745159