The PCM can control polarity of the circuit to control direction of the stepper motor.
IAC Stepper Motor Program: The PCM is also equipped with a memory program that records the number of steps
the IAC stepper motor most recently advanced to during a certain set of parameters. For example: The PCM was
attempting to maintain a 1000 rpm target during a cold start-up cycle. The last recorded number of steps for that
may have been 125. That value would be recorded in the memory cell so that the next time the PCM recognizes the
identical conditions, the PCM recalls that 125 steps were required to maintain the target. This program allows for
greater customer satisfaction due to greater control of engine idle.
Another function of the memory program, which occurs when the power steering switch (if equipped), or the A/C
request circuit, requires that the IAC stepper motor control engine rpm, is the recording of the last targeted steps
into the memory cell. The PCM can anticipate A/C compressor loads. This is accomplished by delaying compressor
operation for approximately 0.5 seconds until the PCM moves the IAC stepper motor to the recorded steps that
were loaded into the memory cell. Using this program helps eliminate idle-quality changes as loads change. Finally,
the PCM incorporates a
9
No-Load
9
engine speed limiter of approximately 1800 - 2000 rpm, when it recognizes that
the TPS is indicating an idle signal and IAC motor cannot maintain engine idle.
A (factory adjusted) set screw is used to mechanically limit the position of the throttle body throttle plate. Never
attempt to adjust the engine idle speed using this screw. All idle speed functions are controlled by the IAC
motor through the PCM.
REMOVAL
3.7L V-6
The Idle Air Control (IAC) motor (3) is located on the
side of the throttle body.
1. Remove air resonator box at throttle body.
2. Disconnect electrical connector from IAC motor.
3. Remove two mounting bolts (screws).
4. Remove IAC motor from throttle body.
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FUEL INJECTION
ND