HOLDEN GEN III V8, Service Training

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GEN III V8 ENGINE MANAGEMENT
TRANSMISSION FLUID PRESSURE MANUAL VALVE POSITION SWITCH ASSEMBLY
This gear range sensing device called a
Transmission Fluid Pressure (TFP) manual valve
position switch assembly is used by the PCM to
sense which gear range has been selected by the
vehicle operator. The TFP manual valve position
switch is located on the valve body and consists of
five pressure switches, two normally closed and
three normally open, combined into one unit.
The normally open fluid pressure switches are the
D4, LO and Reverse fluid pressure switches. They
are normally open and electrical current is stopped
at these switches when no fluid pressure is
present. Fluid pressure moves the diaphragm and
contact element until the contact element touches
both the positive contact and the earth contact.
This creates a closed circuit and allows current to
flow from the positive contact, through the switch
and to earth. The normally closed fluid pressure
switches are the D2 and D3 fluid pressure
switches. They are normally closed and electrical
current is free to flow from the positive contact to
the earth contact when no fluid pressure is present.
Fluid pressure moves the diaphragm to disconnect
the positive and earth contacts. This opens the
switch and stops current from flowing through the
switch.
The PCM applies system voltage to the TFP manual valve position switch assembly on three separate wires. An
open circuit measures 1 2 Volts while an earthed circuit measures 0 Volts. The switches are opened or closed by
fluid pressure. The combination of which switches are open and closed is used by the PCM to determine actual
manual valve position. The TFP manual valve position switch assembly however cannot distinguish between
park and neutral because the monitored valve body pressures are identical in both cases.
LO This switch will have hydraulic pressure
applied to it in manual 1st gear only and will
be closed.
REV This switch will have hydraulic pressure
applied to it in reverse only and will be
closed.
D2 This switch will have hydraulic pressure
applied to it in manual 1 st and 2nd gear and
will be open.
D3 This switch will have hydraulic pressure
applied to it in manual 1 st, 2nd and 3rd gear
and will be open.
D4 This switch will have hydraulic pressure
applied to it in all drive gears except reverse
and will be closed.
These TFP manual valve position switch inputs are used to help control line pressure, torque converter clutch
apply and shift solenoid operation. To monitor TFP manual valve position switch operation, the PCM compares
the actual voltage combination of the switches to a TFP manual valve position switch combination chart stored
in its memory.
There are two possible combinations of the switches within the TFP manual valve position switch assembly that
do not represent an actual gear range. If either of these combinations are detected by the PCM, DTC 1 8 1 0 will
set. DTC 1 8 1 0 will also set if a valid gear range combination appears at the wrong time.
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