Grand Cherokee 2WD V6-3.7L (2008)
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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 sensor
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 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
5 VOLT SUPPLIES
Two different Powertrain Control Module (PCM) five volt supply circuits are used; primary and secondary.
Ignition Circuit Sense
IGNITION CIRCUIT SENSE
This circuit ties the ignition switch to the Powertrain Control Module (PCM). Battery voltage is supplied to the PCM through the ignition switch when
the ignition is in the Run or Start position. This is referred to as the "ignition sense" circuit and is used to "wake up" the PCM.
Power Grounds
POWER GROUNDS
The Powertrain Control Module (PCM) has 2 main grounds. Both of these grounds are referred to as power grounds. All of the high-current, noisy,
electrical devices are connected to these grounds as well as all of the sensor returns. The sensor return comes into the sensor return circuit, passes
through noise suppression, and is then connected to the power ground.
The power ground is used to control ground circuits for the following PCM loads:
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Generator field winding
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Fuel injectors
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Ignition coil(s)
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Certain relays/solenoids
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Certain sensors
