Hummer H1 Service Manual page 203

5-4 Transmission/Transfer Case
CONVERTER
CLUTCH
SOLENOID
TRANSMISSION FLUID PRESSURE MANUAL
VALVE POSITION SWITCH
The pressure switch assembly is mounted on the valve body. It
contains five pressure switches in circuit with the PCM
(Figure 5-4). The switches are used to signal the PCM which
gear range has been selected.
Each pressure switch is activated by fluid pressure
(Figure 5-5). Fluid flow through the manifold is controlled by
the valve body manual valve (Figure 5-6).
The five pressure switches are closed only when fluid pressure
is applied. Fluid flow into the switch cavity presses the dia-
phragm downward against the contact element and switch con-
tact (Figure 5-4). Once the switch closes, it completes the
ground circuit to the PCM through one of the connector pins
(Figure 5-4).
The hydraulic and electrical schematics in Figure 5-6 illustrate
switch activation and fluid flow in third gear. The Drive and
PRND 4/3 switches are pressurized closing the circuit to con-
nector pin C (Figure 5-4). This changes the digital logic at Pin
C to O and the logic at Pins A and B to 1 (Figure 5-6). The
PCM reads this as third gear.
______________________________________________
FLUID
TEMPERATURE
SENSOR
PRESSURE
CONTROL
SOLENOID
Figure 5-3: Transmission Shift Control Components
INPUT
SPEED
SENSOR
SHIFT
PRESSURE
SOLENOIDS
SWITCH
ASSEMBLY
PRND 4/3
REVERSE
SWITCH
SWITCH
PRESSURE
PRND 4
SWITCH
SWITCH
ASSEMBLY
Figure 5-4: Pressure Switch and Connector
Identification
THREE PIN
CONNECTOR
LO (1-2)
SWITCH
DRIVE
SWITCH
®