Wagoneer L6-242 4.0L VIN L FI (1989)
^
Speed sensor
^
Sync signal
^
Throttle position sensor (TPS)
Based on these inputs the following occurs:
^
Voltage is applied to the fuel injectors with the ECU controlling the injection sequence and injector pulse width.
^
The ECU monitors the oxygen sensor input and adjusts air/fuel ratio, adjusts engine idle speed, and controls ignition timing. The ECU
adjusts the air/fuel ratio by controlling the injector pulse width, adjusts the engine idle speed by controlling the idle speed stepper motor,
and adjusts the ignition timing through the ignition control module.
^
The ECU operates the A/C compressor clutch through the compressor clutch relay (the A/C has to have been previously selected by the
vehicle operator and requested by the A/C thermostat).
^
The ECU breaks the ground path for the EGR valve solenoid allowing vacuum to reach the EGR valve transducer in anticipation of
EGR operation.
Deceleration
This is an OPEN LOOP mode. During hard deceleration, when the engine is at operating temperature, the ECU receives the following inputs:
^
Air conditioning select signal (if equipped)
^
Air conditioning request signal (if equipped)
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Battery voltage
^
Coolant temperature sensor
^
Gear indicator signal (auto. trans. only)
^
Manifold air temperature (MAT) sensor
^
Manifold absolute pressure (MAP) sensor
^
Speed sensor
^
Sync signal
^
Throttle position sensor (TPS)
If the vehicle is under hard deceleration with the proper RPM and closed throttle conditions, the ECU will ignore the oxygen sensor input signal and
enter a fuel cut-off strategy in which it will not supply battery voltage to the injectors (this is done to ensure that an exhaust back-fire doesn't occur, and
that emission levels are kept down). If a hard deceleration does not exist, the ECU will determine the proper injector pulse width and continue injection.
Based on the above inputs the ECU will adjust engine idle speed through the idle speed stepper motor, ignition timing through the ignition control
module, and energize the EGR valve solenoid to prevent EGR operation.
Wide Open Throttle
This is an OPEN LOOP mode. During wide open throttle operation the ECU receives the following inputs:
^
Battery voltage
^
Coolant temperature sensor
^
Knock sensor
^
Manifold air temperature (MAT) sensor
^
Manifold absolute pressure (MAP) sensor
^
Throttle position sensor (TPS)
^
Speed sensor
^
Sync signal
During wide open throttle conditions the following occurs:
^
The fuel pump relay and ballast resistor are bypassed and battery voltage is applied to the fuel pump through the oxygen sensor heater
relay.
^
Voltage is applied to the fuel injectors with the ECU controlling the injection sequence and injector pulse width.
^
The ECU ignores the oxygen sensor input signal and provides a predetermined amount of additional fuel by adjusting injector pulse
width.
^
The oxygen sensor heater relay is energized by the ECU causing the relay switch to open and stop power to the oxygen sensor heating
element.
^
The ECU adjusts ignition timing through the ignition control module, energizes the EGR valve solenoid to restrict EGR operation, and
disengages the A/C compressor clutch through the clutch relay for approximately 15 seconds.
^
If the vehicle has a manual transmission, the upshift light is operated by the ECU.
Ignition Switch OFF
The ECU performs a number of functions after the ignition switch is turned OFF, and the following is a list of those functions:
