Description & Operation
The ASD relay is located in the PDC. The inside top of the PDC cover has a label showing relay and fuse location. The Automatic Shutdown (ASD) relay supplies battery voltage to the fuel injectors, electronic ignition coil and the heating elements in the oxygen sensors generator field and PCM sense circuit.
A bus bar in the Power Distribution Center (PDC) supplies voltage to the solenoid side and contact side of the relay. The ASD relay power circuit contains a fuse between the buss bar in the PDC and the relay. The fuse also protects the power circuit for the fuel pump relay and pump. The fuse is located in the PDC.
The PCM controls the relay by switching the ground path for the solenoid side of the relay on and off. The PCM turns the ground path off when the ignition switch is in the OFF position unless the O2 Heater Monitor test is being run. When the ignition switch is in the ON or CRANK position, the PCM monitors the Crankshaft Position Sensor and Camshaft Position Sensor signals to determine engine speed and ignition timing (coil dwell). If the PCM does not receive the Crankshaft Position Sensor and Camshaft Position Sensor signals when the ignition switch is in the RUN position, it will de-energize the ASD relay.
|AUTO SHUTDOWN RELAY PINS, COLORS & FUNCTION TABLE|
|34||A14 18RD/WT||Fused B+|
|35||A15 18RD/WT||Fused B+|
|36||A142 18DG/OR||Automatic Shutdown Relay|
|38||K51 18DB/YL||Automatic Shutdown Relay|
Auto Shutdown relay pins, colors and functions chart
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. If the PCM does not receive 12 volts from this input after grounding the ASD relay, it sets a diagnostic trouble code (DTC).