2002 Ford Expedition

Check or replace the ignition switch !

IGNITION SWITCH
To inspect ignition switch for mechanical operation, rotate lock cylinder through all switch positions. If lock cylinder does not bind and returns from START to RUN position without assistance, go to next step. If binding occurs or switch does not return from START or RUN positions, lock cylinder and ignition switch should either be disassembled and inspected for damage, or ignition switch should be replaced.
To test electrical function of ignition switch, disconnect ignition switch harness connector. Check resistance between specified switch terminals. See Fig. 4. See IGNITION SWITCH CONTINUITY table. If resistance is not as specified, replace ignition switch.

IGNITION SWITCH CONTINUITY
Switch Position. Continuity Between Terminals
Start.B4 & STA; B5 & I1
Run.A1 & B1; A3 & B3;
. A4 & B4; B5 & I1
Accessory.A1 & B5