Vehicle speed and distance-pcm input. Auto shutdown (asd) relay-pcm output

Vehicle speed and distance-pcm input


Vehicle speed and distance covered are measured by the Rear Wheel Speed Sensor. The sensor is mounted to the rear axle. A signal is sent from this sensor to the Controller Antilock Brake (CAB) computer.

A signal is then sent from the CAB to the Powertrain Control Module (PCM) to determine vehicle speed and distance covered. The PCM will then determine strategies for fuel system and speed control system operation.

Refer to Odometer and Trip Odometer in Group 8E, Instrument Panel for additional information.

Auto shutdown (asd) relay-pcm output


The 5-pin, 12-volt, Automatic Shutdown (ASD) relay is located in the Power Distribution Center (PDC). Refer to label on PDC cover for relay location.


The ASD relay supplies battery voltage (12+ volts) to the fuel injectors and ignition coil(s). With certain emissions packages it also supplies 12-volts to the oxygen sensor heating elements.

The ground circuit for the coil within the ASD relay is controlled by the Powertrain Control Module (PCM). The PCM operates the ASD relay by switching its ground circuit on and off.

The ASD relay will be shut-down, meaning the 12-volt power supply to the ASD relay will be de-activated by the PCM if:

  • the ignition key is left in the ON position. This is if the engine has not been running for approximately 1.8 seconds.
  • there is a crankshaft position sensor signal to the PCM that is lower than pre-determined values

The PCM will sense if or when the ASD relay has been activated through a "sense circuit". Refer to Automatic Shut-Down (ASD) Relay Sense-PCM Input for additional information.

    Dodge Durango (DN) 1998-2003 Service Manual


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