Grand Cherokee 4WD L6-242 4.0L VIN S MFI (1993)
-
Apply voltage to the injectors. The PCM then controls injection sequence and pulse width by switching individual injector ground paths on and
off.
-
Adjust engine idle speed through the IAC motor.
-
Adjust ignition timing.
-
Operate A/C Compressor Clutch relay (if equipped and selected).
-
Operate the Up-Shift indicator light.
-
Begin to monitor oxygen sensor. When engine is at operating temperature, the system will leave warm up mode and go into closed loop
operation.
Idle
THIS IS A CLOSED LOOP MODE.
With engine idling at operating temperature, the Powertrain Control Module (PCM) receives inputs from:
-
Air Conditioning Control Position (if equipped)
-
Battery voltage
-
Camshaft position (CMP) sensor
-
Engine coolant temperature (ECT) sensor
-
Manifold absolute pressure (MAP) sensor
-
Intake air temperature (IAT) sensor
-
Crankshaft position (CMP) sensor
-
Throttle Position Sensor (TPS)
-
Heated oxygen sensor (HO2S)
Based on these inputs the PCM will:
-
Apply voltage to the injectors. The PCM then controls injection sequence and pulse width by switching individual injector ground paths on and
off.
-
Monitor oxygen sensor and fine tune air/fuel ratio by varying injector pulse width.
-
Adjust engine idle speed through the IAC motor.
-
Adjust ignition timing.
-
Operate A/C Compressor Clutch relay (if equipped and selected).
Ignition Switch Off
WHEN THE IGNITION SWITCH IS OFF THE POWERTRAIN CONTROL MODULE (PCM) WILL STOP OPERATING THE:
-
Fuel injectors
-
Ignition coil
-
ASD relay
-
Fuel pump relay.
Ignition Switch On
THIS IS AN OPEN LOOP MODE.
When the Powertrain Control Module (PCM) is ACTIVATED by the ignition switch, the following actions occur:
-
The PCM preposition the idle air control (IAC) motor.
-
The PCM reads atmospheric air pressure from the manifold absolute pressure (MAP) sensor and calculates the basic fuel strategy.
-
The PCM monitors the throttle position sensor (TPS) and engine coolant temperature (ECT) sensor input. The PCM uses these inputs to
