Cherokee 4WD L6-242 40L VIN M FI (1988) Powertrain Control Module Diagrams
This is an OPEN LOOP mode. During engine warm-up the ECU receives inputs from:
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Air conditioning select signal (if equipped)
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Air conditioning request signal (if equipped)
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Battery voltage
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Coolant temperature sensor
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Knock sensor
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Manifold air temperature (MAT) sensor
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Manifold absolute pressure (MAP) sensor
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Neutral Safety Switch (Gear indicator signal-automatic transmission only)
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Speed sensor
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Sync signal
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Throttle position sensor (TPS)
Based on these inputs the following occurs:
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Voltage is applied to the fuel injectors with the ECU controlling the injection sequence and injector pulse width.
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The ECU adjusts engine idle speed through the idle speed stepper motor and ignition timing through the ignition control module.
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The ECU energizes the EGR valve solenoid to restrict EGR operation, and operates the A/C compressor clutch through the clutch relay
(this only occurs if A/C has been selected by the vehicle operator and requested by the A/C thermostat).
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If the vehicle has a manual transmission, the upshift light is operated by the ECU.
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When the engine has reached operating temperature the ECU will begin monitoring the oxygen sensor input, the system will leave the
warm-up mode and go into closed loop operation.
Idle
This is a CLOSED LOOP mode. At idle speed with the engine at operating temperature, the ECU receives inputs from:
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Air conditioning select signal (if equipped)
-
Air conditioning request signal (if equipped)
-
Battery voltage
-
Coolant temperature sensor
-
Knock sensor
-
Manifold air temperature (MAT) sensor
-
Manifold absolute pressure (MAP) sensor
-
Neutral Safety Switch (Gear-indicator signal automatic transmission only)
-
Oxygen sensor
-
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 length of injection
time).
-
The ECU monitors the 02 sensor input and uses that information to adjust air/fuel ratio, engine idle speed, and 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 energizes the EGR valve solenoid to restrict EGR operation.
-
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).
Cruise
This is a CLOSED LOOP mode. At cruising speed with the engine at operating temperature, the ECU receives inputs from:
-
Air conditioning select signal (if equipped)
-
Air conditioning request signal (if equipped)
-
Battery voltage
-
Coolant temperature sensor
-
Gear indicator signal (auto. trans. only)
-
Knock sensor
-
Manifold air temperature (MAT) sensor
-
Manifold absolute pressure (MAP) sensor
-
Oxygen sensor
