Grand Cherokee 2WD L6-4.0L VIN S (1997)
Fig. 9 Throttle Body & Sensors
The IAC motor is mounted on the throttle body and is controlled by the powertrain control module (PCM).
The throttle body has an air control passage that provides air for the engine at idle (the throttle plate is closed). The IAC motor pintle protrudes
into the air control passage and regulates air flow through it. Based on various sensor inputs, the 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 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 PCM.
Ignition Coil
IGNITION COIL-PCM OUTPUT
System voltage is supplied to the ignition coil positive terminal. The Powertrain Control Module (PCM) operates the ignition coil. Base (initial)
ignition timing is not adjustable. The PCM adjusts ignition timing to meet changing engine operating conditions.
Fig. 19 Ignition Coil - 4.0
The ignition coil is located near the distributor.
Leak Detection Pump, Evaporative System
LEAK DETECTION PUMP-PCM OUTPUT
Certain California models are equipped with a Leak Detection Pump (LDP). The LDP is activated through this PCM output.
Malfunction Indicator (Check Engine) Lamp
MALFUNCTION INDICATOR (CHECK ENGINE) LAMP-PCM OUTPUT
The malfunction indicator lamp illuminates each time the ignition key is turned on. It will stay on for approximately three seconds as a bulb test.
The lamp is displayed on the instrument panel as the CHECK ENGINE lamp.
