Cherokee 2WD L4-150 2.5L VIN H TBI (1988)
The ECU provides a ground path for the injector enabling it to precisely control injector pulse width. The ECU controls engine idle speed, ignition
timing, and throttle stop angle. For vehicles equipped with a manual transmission, the up-shift indicator light is controlled by the ECU according to
engine speed and load.
CRUISE
When the engine is at operating temperature this condition is considered a CLOSED LOOP mode. During cruising speed the following inputs are
received by the ECU:
-
A/C control positions
-
Coolant temperature
-
Engine speed
-
Exhaust gas oxygen content
-
Gear position (automatic transmission)
-
Manifold air/fuel temperature
-
Manifold absolute pressure
-
Throttle position
The ECU provides a ground path for the injector enabling it to precisely control injector pulse width. The ECU controls engine idle speed, ignition
timing, and throttle stop angle. The ECU controls the air/fuel mixture ratio according to the oxygen content in the exhaust gas. For vehicles equipped
with a manual transmission, the up-shift indicator light is controlled by the ECU according to engine speed and load.
DECELERATION
This is a CLOSED LOOP mode. During deceleration the following inputs are received by the ECU:
-
A/C control positions
-
Coolant temperature
-
Engine speed
-
Exhaust gas oxygen content
-
Gear position (automatic transmission)
-
Manifold air/fuel temperature
-
Manifold absolute pressure
-
Throttle position
When the ECU receives input from the closed throttle switch informing it that the engine is decelerating, it will provide a ground path for the EGR valve
vacuum solenoid. When grounded, the solenoid interrupts the flow of vacuum to the EGR valve, resulting in no EGR flow. The ECU provides a ground
path for the injector to precisely control the injector pulse width. During rapid deceleration the ECU may stop all fuel injection for a short period of time
to reduce the chance of an exhaust back-fire and to reduce tale pipe emissions. The ECU controls engine idle speed and throttle stop angle during this
mode.
WIDE OPEN THROTTLE
This is an OPEN LOOP mode. During wide-open throttle operation, the following inputs are received by the ECU:
-
Coolant temperature
-
Manifold air/fuel temperature
-
Manifold absolute pressure
-
Engine speed
-
Throttle position
When the ECU receives wide open throttle input from the TPS, it will provide a ground path for the EGR valve vacuum solenoid. When grounded, the
solenoid interrupts the flow of vacuum to the EGR valve stopping EGR function. The exhaust gas oxygen content input is not accepted by the ECU and
it will ground the injector to precisely control a predetermined amount of additional fuel.
IGNITION SWITCH OFF
This is an OPEN LOOP mode. When the ignition switch is turned to the OFF position, the ECU ceases to provide a ground path for the injector and all
fuel injection stops. Current is supplied to the ISA motor through the B+ Latch relay for 3 to 5 seconds enabling the ECU to extend the ISA for the next
start-up. The ECU then deactivates.
