P1389
No ASD Relay Output Voltage At PCM
No Z1 or Z2 voltage sensed when the auto shutdown relay is energized.
AUTO SHUT DOWN RELAY
DESCRIPTION
The 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
OPERATION
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.
|