Wrangler 4WD L4-150 2.5L VIN P MFI (1998)
Automatic Shut Down (ASD) Relay: Description and Operation
LOCATION
Relay is mounted in the power distribution center.
PURPOSE
Relay supplies battery voltage to fuel pump relay, fuel injectors, ignition coil, and O2 sensor heating element when energized by Powertrain
Control Module (PCM).
OPERATION
The PCM energizes Auto Shutdown (ASD) relay by supplying relay ground, when ignition switch is in START or RUN position and PCM is
receiving a reference signal from distributor.
When the ground is applied, the relay is energized, and voltage is allowed to flow to fuel pump, fuel injectors, ignition coil, and O2 sensor heating
element.
When PCM does not receive reference signal from ignition system, (indicating engine is not running), then the PCM interrupts relay ground circuit
and no voltage is supplied to fuel pump, fuel injectors, ignition coil, and O2 sensor heating element.
The PCM controls fuel pump relay and ASD relay simultaneously, through same ground circuit.
CIRCUIT OPERATION
When the ignition switch is in either the START or RUN position, it connects circuit A1 from fuse 3 in the Power Distribution Center (PDC) to
circuit A21. Circuit A21 feeds circuit F12 through fuse 11 in the fuse block. Circuit F12 powers the coil side of the Automatic Shut Down (ASD)
relay. The Powertrain Control Module (PCM) provides ground for the relay coil on circuit K51. Circuit K51 connects to cavity C3 of the PCM.
When the PCM grounds the ASD relay, contacts inside the relay close and connect circuit A14 from fuse 6 in the PDC to circuit A142. Circuit
A142 splices to the fuel injectors, ignition coil and the upstream and downstream heated oxygen sensors. Circuit A142 also connects to cavity C12
of the PCM.
