Dodge Dakota Sport 2001 Service Manual page 558

AN
SWITCH (Continued)
Multiplexing
The PCM sends out 5 volts through a fixed resistor
and monitors the voltage change between the fixed
resistor and the switches. If none of the switches are
depressed, the PCM will measure 5 volts at the sen-
sor point (open circuit). If a switch with no resistor is
closed, the PCM will measure 0 volts (grounded cir-
cuit). Now, if a resistor is added to a switch, then the
PCM will measure some voltage proportional to the
size of the resistor. By adding a different resistor to
each switch, the PCM will see a different voltage
depending on which switch is pushed.
Another resistor has been added to the 'at rest cir-
cuit' causing the PCM to never see 5 volts. This was
done for diagnostic purposes. If the switch circuit
should open (bad connection), then the PCM will see
the 5 volts and know the circuit is bad. The PCM will
then set an open circuit fault.
REMOVAL
WARNING: BEFORE BEGINNING ANY AIRBAG SYS-
TEM COMPONENT REMOVAL OR INSTALLATION,
REMOVE AND ISOLATE THE NEGATIVE (-) CABLE
FROM THE BATTERY. THIS IS THE ONLY SURE
WAY TO DISABLE THE AIRBAG SYSTEM. THEN
WAIT TWO MINUTES FOR SYSTEM CAPACITOR TO
DISCHARGE BEFORE FURTHER SYSTEM SERVICE.
FAILURE TO DO THIS COULD RESULT IN ACCIDEN-
TAL AIRBAG DEPLOYMENT
INJURY.
(1) Disconnect and isolate negative battery cable.
(2) Remove airbag module. Refer to 8, Passive
Restraint Systems for procedures.
(3) Remove switch-to-steering
screws (Fig. 8).
(4) Remove switch.
(5) Remove electrical connector at switch.
INSTALLATION
(1) Install electrical connector to switch.
(2) Install switch and mounting screws.
(3) Tighten screws to 1.5 N·m (14 in. lbs.) torque.
(4) Install airbag module. Refer to 8, Passive
Restraint Systems for procedures.
(5) Connect negative battery cable.
VACUUM RESERVOIR
DESCRIPTION
nected to an engine vacuum source by vacuum lines.
AND POSSIBLE
OPERATION
uum needed to maintain proper speed control opera-
tion when engine vacuum drops, such as in climbing
a grade while driving. A one-way check valve is used
wheel mounting
in the vacuum line between the reservoir and the
vacuum source. This check valve is used to trap
engine vacuum in the reservoir. On certain vehicle
applications, this reservoir is shared with the heat-
ing/air-conditioning system. The vacuum reservoir
cannot be repaired and must be replaced if faulty.
DIAGNOSIS AND TESTING - VACUUM SUPPLY
TEST
and install a vacuum gauge into the disconnected
hose.
uum gauge should read at least ten inches of mer-
cury.
Fig. 8 Speed Control Switches
1 - MOUNTING SCREWS (2)
2 - SPEED CONTROL SWITCHES (2)
The vacuum reservoir is a plastic storage tank con-
The vacuum reservoir is used to supply the vac-
(1) Disconnect vacuum hose at speed control servo
(2) Start engine and observe gauge at idle. Vac-
SPEED CONTROL 8P - 7