ASD
CF Veteran
Joined: Aug 2010
Posts: 8,357
Likes: 103
From: Canton, MI
Year: 1999
Model: Cherokee
Engine: 4.0
The ASD relay is used by the PCM to supply voltage to fuel
pump, fuel injectors and ignition coil. The relay contacts are
normally open. Power is supplied to relay coil when the ignition switch is
turned on. The PCM controls the ground circuit, which energizes the coil and closes the relay contacts.
The PCM will only ground the relay when ignition switch is in the RUN or START positions and activity is sensed through the crankshaft position sensor and the camshaft position sensor. If the PCM senses the RPM signal has stopped, it will remove the ground from relay coil, which will cause the contacts to open and remove power from the circuit.
pump, fuel injectors and ignition coil. The relay contacts are
normally open. Power is supplied to relay coil when the ignition switch is
turned on. The PCM controls the ground circuit, which energizes the coil and closes the relay contacts.
The PCM will only ground the relay when ignition switch is in the RUN or START positions and activity is sensed through the crankshaft position sensor and the camshaft position sensor. If the PCM senses the RPM signal has stopped, it will remove the ground from relay coil, which will cause the contacts to open and remove power from the circuit.
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