The idle speed control (ISC) motor is attached to the throttle body fuel injection (TBI) unit. The powertrain control module (PCM) uses the ISC motor in order to control engine idle speed. The ISC motor consists of the following components:

The PCM controls the engine idle speed by running the ISC motor plunger forward or backward. The ISC motor plunger contacts the throttle lever screw in order to control the throttle valve opening. Forward movement of the ISC motor plunger increases the throttle valve opening and increases engine (idle) speed. Backward movement of the ISC motor plunger decreases the throttle valve opening and lowers engine (idle) speed.

The engine idle speed is controlled by the powertrain control module (PCM) through the idle speed control (ISC) motor. There are several reasons for idle speed control:

1. Maintain the engine idle speed at the specified RPM at all times. The engine idle speed can vary due to any of the following reasons:

•	A change in the load applied to engine (when an electrical load is applied, the automatic transaxle is shifted to R, D, 2 or L ranges, the A/C is turned ON, the headlights or stop lights are turned ON, etc.).

•	A change in the atmospheric pressure.

•	A change in the engine's condition over time.

•	Other factors causing the idle speed to change.

2. Improve the starting performance of the engine.
3. Improve the driveability of the engine during warm up.
4. Compensate for the change in the air/fuel mixture ratio when decelerating (dash-pot effect).

The ISC motor opens and closes the throttle valve according to signals from the PCM. The PCM determines the correct engine idle speed by using input from various sensors and switches in order to assess engine status and requirements. When a forward rotation signal is sent from the PCM to the ISC motor, the ISC motor plunger extends in order to open the throttle valve. When a reverse rotation signal is sent, the ISC motor plunger contracts and the throttle valve closes by the return spring force. How much the throttle valve opens or closes is controlled according to the time during which signals are transmitted from the PCM to the ISC motor. The longer the time interval, the larger the throttle valve movement.

(1)	Main Relay
(2)	Relay Box

The main relay is controlled by the powertrain control module (PCM). The PCM provides an electrical ground for the coil of the main relay when the ignition is ON or when the engine is running. The main relay provides power to many of the engine control components including the PCM. The following is a list of some of the PCM controlled outputs that depend on the main relay for proper operation:

•	The ignition system

•	The fuel injector

•	The fuel pump

•	The Exhaust Gas Recirculation (EGR) system solenoids

•	The EVAP Control system solenoids

•	The Idle Speed Control (ISC) relay

•	The Early Fuel Evaporation (EFE) relay

The main relay is located in the relay box on the LH side of the engine compartment near the battery.

Malfunction Indicator Lamp (MIL)

The malfunction indicator lamp (MIL) is located in the instrument panel gauge cluster. The MIL is illuminated by the powertrain control module (PCM) in order to notify the vehicle operator of an engine control system malfunction.

The MIL receives ignition positive voltage anytime the ignition is ON. The PCM illuminates the MIL by providing a ground for the MIL circuit. The MIL should be illuminated whenever the ignition is ON and the engine is not running. Illuminating the MIL whenever the ignition is ON and the engine is not running provides a check of the bulb and circuit. The PCM will turn OFF the MIL once the engine is started or running if there are no engine control system malfunctions.

Many of the conditions for illuminating and extinguishing of the MIL are performed by the PCM in accordance with OBD II regulations. For more information on the MIL function, review Powertrain Control Module (Common OBD II Systems).

The Powertrain On-Board Diagnostic (OBD) System Check guides the user to the correct diagnosis and repair of the MIL circuit.

Up-Shift Indicator Lamp

The upshift indicator lamp is located in the instrument panel cluster assembly and is controlled by the powertrain control module. The purpose of the upshift indicator is to provide a display that indicates to the driver when to upshift the manual transaxle for optimum fuel economy. The powertrain control module determines the optimal upshift point based on engine speed and load. The upshift indicator lamp will not be operational under any of the following conditions:

•	The vehicle's speed is less than 5 km/h (3 MPH).

•	The engine is idling or the engine is running under a heavy load.

•	The engine's speed is less than 1500 RPM.

Duty Check Data Link Connector