Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Auto Shutdown (ASD) Relay
ASD relay provides battery voltage to alternator field winding, electric fuel pump, fuel injectors, ignition coil and oxygen sensor heating element. PCM controls ASD relay by switching ASD relay ground circuit on and off. ASD relay is located inside Power Distribution Center (PDC), which is located in engine compartment. See label on PDC cover for relay and fuse identification.
PCM determines engine speed and synchronizes injectors from distributor pick-up signal. If Crankshaft Position (CKP) signal is not received when ignition switch is in RUN or START position, PCM opens ASD relay ground circuit. ASD relay turns off battery voltage to alternator field winding, electric fuel pump, fuel injectors, ignition coil and O2S heating element.
If ASD relay has a suspected malfunction, replace with a known-good part and retest. If malfunction is still present, see TESTS W/CODES - 3.9L article in the ENGINE PERFORMANCE section.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.