Chrysler PT Cruiser 2001 Service Manual Supplement page 1122

PT
DESCRIPTION AND OPERATION (Continued)
OPERATION
All vehicles use a proportional purge solenoid. The
solenoid regulates the rate of vapor flow from the
EVAP canister to the throttle body. The PCM oper-
ates the solenoid.
During the cold start warm-up period and the hot
start time delay, the PCM does not energize the sole-
noid. When de-energized, no vapors are purged.
The proportional purge solenoid operates at a fre-
quency of 200 hz and is controlled by an engine con-
troller circuit that senses the current being applied
to the proportional purge solenoid and then adjusts
that current to achieve the desired purge flow. The
proportional purge solenoid controls the purge rate of
fuel vapors from the vapor canister and fuel tank to
the engine intake manifold.
IDLE AIR CONTROL MOTOR—PCM OUTPUT
DESCRIPTION
The Idle Air Control (IAC) motor is mounted on the
throttle body. The PCM operates the idle air control
motor (Fig. 13).
Fig. 13 Idle Air Control Motor—2.4L
1 – IAC
2 – PCM
3 – TPS
OPERATION
The PCM adjusts engine idle speed through the
idle air control motor to compensate for engine load,
coolant temperature or barometric pressure changes.
The throttle body has an air bypass passage that
provides air for the engine during closed throttle idle.
The idle air control motor pintle protrudes into the
air bypass passage and regulates air flow through it.
The PCM adjusts engine idle speed by moving the
IAC motor pintle in and out of the bypass passage.
The adjustments are based on inputs the PCM
receives. The inputs are from the throttle position
sensor, crankshaft position sensor, coolant tempera-
ture sensor, MAP sensor, vehicle speed sensor and
various switch operations (brake, park/neutral, air
conditioning).
When engine rpm is above idle speed, the IAC is
used for the following functions:
• Off-idle dashpot
• Deceleration air flow control
• A/C compressor load control (also opens the pas-
sage slightly before the compressor is engaged so
that the engine rpm does not dip down when the
compressor engages)
Target Idle
Target idle is determined by the following inputs:
• Gear position
• ECT Sensor
• Battery voltage
• Ambient/Battery Temperature Sensor
• VSS
• TPS
• MAP Sensor
DATA LINK CONNECTOR
DESCRIPTION
The data link connector is located inside the vehi-
cle, under the instrument panel, at the driver's kick
panel (Fig. 14).
Fig. 14 Data Link (Diagnostic) Connector
1 – DATA LINK CONNECTOR
FUEL SYSTEM 14 - 35