RAM 1500 Truck 4WD V8-5.9L VIN Z (2002)
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The PCM monitors the O(2)S sensor input and adjusts air-fuel ratio. It also adjusts engine idle speed through the idle air control (IAC) motor.
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The PCM adjusts ignition timing by turning the ground path to the coil(s) ON and OFF.
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The PCM operates the A/C compressor clutch through the clutch relay This happens if A/C has been selected by the vehicle operator and
requested by the A/C thermostat.
Acceleration Mode
This is an Open Loop mode. The PCM recognizes an abrupt increase in throttle position or MAP pressure as a demand for increased engine output
and vehicle acceleration. The PCM increases injector pulse width in response to increased throttle opening.
Deceleration Mode
When the engine is at operating temperature, this is an Open Loop mode. During hard deceleration, the PCM receives the following inputs.
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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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Engine coolant temperature sensor
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Crankshaft position sensor
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Intake manifold air temperature sensor
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Manifold absolute pressure (MAP) sensor
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Throttle position sensor (TPS)
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Camshaft position sensor signal
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Park/neutral switch (gear indicator signal-auto. trans. only)
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Vehicle speed
If the vehicle is under hard deceleration with the proper rpm and closed throttle conditions, the PCM will ignore the oxygen sensor input signal. The
PCM will enter a fuel cut-OFF strategy in which it will not supply a ground to the injectors. If a hard deceleration does not exist, the PCM will
determine the proper injector pulse width and continue injection.
Based on the above inputs, the PCM will adjust engine idle speed through the idle air control (IAC) motor.
The PCM adjusts ignition timing by turning the ground path to the coil ON and OFF.
Wide Open Throttle Mode
This is an Open Loop mode. During wide open throttle operation, the PCM receives the following inputs.
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Battery voltage
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Crankshaft position sensor
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Engine coolant temperature sensor
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Intake manifold air temperature sensor
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Manifold absolute pressure (MAP) sensor
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Throttle position sensor (TPS)
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Camshaft position sensor signal
During wide open throttle conditions, the following occurs:
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Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then control the injection sequence and injector pulse width
by turning the ground circuit to each individual injector ON and OFF. The PCM ignores the oxygen sensor input signal and provides a
predetermined amount of additional fuel. This is done by adjusting injector pulse width.
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The PCM adjusts ignition timing by turning the ground path to the coil(s) ON and OFF.
Ignition Switch OFF Mode
When ignition switch is turned to OFF position, the PCM stops operating the injectors, ignition coil, ASD relay and fuel pump relay.
5 VOLT SUPPLIES
Two different Powertrain Control Module (PCM) five volt supply circuits are used; primary and secondary
Primary 5-volt supply:
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supplies the required 5 volt power source to the Crankshaft Position (CKP) sensor.
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supplies the required 5 volt power source to the Camshaft Position (CMP) sensor.
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supplies a reference voltage for the Manifold Absolute Pressure (MAP) sensor.
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supplies a reference voltage for the Throttle Position Sensor (TPS) sensor.
Secondary 5-volt supply:
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supplies the required 5 volt power source to the oil pressure sensor.
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supplies the required 5 volt power source for the Vehicle Speed Sensor (VSS) (if equipped).
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supplies the 5 volt power source to the transmission pressure sensor (certain automatic transmissions).
IGNITION CIRCUIT SENSE
This circuit ties the ignition switch to the Power- train Control Module (PCM).
