Grand Caravan FWD V6-3.3L VIN 3 Flex Fuel (2002)
Main Relay (Computer/Fuel System): Description and Operation
The Auto Shut Down (ASD) relay is located in the Power Distribution Center (PDC). For the location of the relay within the PDC, refer to the PDC
cover for location. Check electrical terminals for corrosion and repair as necessary
The ASD sense circuit informs the PCM when the ASD relay energizes. A 12 volt signal at this input indicates to the PCM that the ASD has been
activated. This input is used only to sense that the ASD relay is energized.
When energized, the ASD relay supplies battery voltage to the fuel injectors, ignition coils and the heating element in each oxygen sensor.
When energized, the ASD relay provides power to operate the injectors, ignition coil, generator field, O2 sensor heaters (both upstream and
downstream), (EGR solenoid and PCV heater if equipped) and also provides a sense circuit to the PCM for diagnostic purposes. If the PCM does not
receive 12 volts from this input after grounding the ASD relay, it sets a Diagnostic Trouble Code (DTC). The PCM energizes the ASD any time there is
a Crankshaft Position sensor signal that exceeds a predetermined value. The ASD relay can also be energized after the engine has been turned OFF to
perform an O2 sensor heater test, if vehicle is equipped with OBD II diagnostics.
As mentioned earlier, the PCM energizes the ASD relay during an O2 sensor heater test. This test is performed only after the engine has been shut off.
The PCM still operates internally to perform several checks, including monitoring the O2 sensor heaters.
