Chrysler DODGE D150 1993 Service Manual page 855

trol (IAC) stepper motor position to compensate for
increased engine load from the A/C compressor.
By switching the ground path for the relay on and
off, the PCM is able to cycle the A/C compressor
clutch. This is based on changes in engine operating
conditions. If, during A/C operation, the PCM senses
low idle speeds or a wide open throttle condition, it
will de-energize the relay. This prevents A/C clutch
engagement. The relay will remain de-energized un­
til the idle speed increases or the wide open throttle
condition exceeds 15 seconds or no longer exists. The
PCM will also de-energize the relay if coolant tem­
perature exceeds 125°C (257°F).
IDLE AIR CONTROL (IAC) MOTOR-PCM OUTPUT
The IAC motor is mounted to the back of the throt­
tle body (Fig. 13) and is controlled by the powertrain
control module (PCM).
AAANIFOLD ABSOLUTE
PRESSURE SENSOR
MOUNTING SCREWS
MAP SENSOR
THROTTLE
POSITION
SENSOR J9314-86
Fig. 13 IAC Motor—Typical
The throttle body has an air control passage t h a t
provides air for the engine at idle (the throttle plate
is closed). The IAC motor pintle protrudes into the
air control passage (Fig. 14) and regulates air flow
through it. Based on various sensor inputs, the pow­
ertrain control module (PCM) adjusts engine idle
speed by moving the IAC motor pintle in and out of
the air control passage. The IAC motor is positioned
when the ignition key is turned to the On position.
A (factory adjusted) set screw is used to mechani­
cally limit the position of the throttle body throttle
plate. Never attempt to adjust the engine idle
s p e e d u s i n g this screw. All idle speed functions are
controlled by the PCM.
RUBBER FITTING
J9314-87
Fig. 14 Throttle Body Air Control Passage
AUTO SHUT DOWN (ASD) RELAY—PCM OUTPUT
The ASD relay is located in the engine compart­
ment (Fig. 12).
The ASD supplies battery voltage to the fuel pump,
fuel injector, ignition coil, generator field winding
and oxygen ( 0
2
) sensor(s) heating element. The
ground circuit for the coil in the ASD relay is con­
trolled by the powertrain control module (PCM). The
PCM operates the relay by switching the ground cir­
cuit on and off.
The fuel pump relay is controlled by the PCM
through same circuit t h a t the ASD relay is con­
trolled.
GENERATOR F I E L D - P C M OUTPUT
The powertrain control module (PCM) regulates
the charging system voltage within a range of 12.9 to
15.0 volts. Refer to Group 8A for charging system in­
formation.
GENERATOR L A M P - P C M OUTPUT
If the powertrain control module (PCM) senses a
low charging condition in the charging system, it
will illuminate the generator lamp on the instrument
panel. For example, during low idle with all accesso­
ries turned on, the light may momentarily go on.
Once the PCM corrects idle speed to a higher rpm,
the light will go out. Refer to Group 8A for charging
system information.
ELECTRIC EXHAUST GAS RECIRCULATION
TRANSDUCER (EET) S 0 L E N 0 I D - P C M OUTPUT
Refer to Group 25, Emission Control System for in­
formation. See Electric Exhaust Gas Recirculation
Transducer (EET) Solenoid.
SRI L A M P - P C M OUTPUT
The instrument panel mounted service reminder
indicator (SRI) lamp was formerly referred to as the
emission maintenance reminder (EMR) lamp. It is