Grand Cherokee 2WD V8-318 5.2L VIN Y MFI (1994)
- Adjust engine idle speed through the IAC motor.
- Adjust ignition timing.
- Operate A/C Compressor Clutch relay (if 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 PCM receives inputs from:
- Air Conditioning Control Position
- Battery voltage
- Camshaft position (CMP) sensor
- Engine coolant temperature (ECT) sensor
- Manifold absolute pressure (MAP) sensor
- Intake air temperature (IAT) sensor
- Crankshaft position (CKP) 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 selected).
Ignition Switch Off
When the ignition switch is off the 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 SFI system is ACTIVATED by the ignition switch, the following actions occur:
- The PCM prepositions the idle air control (IAC) motor.