P1703

P1703 is a Ford-specific code meaning the Brake On/Off (BOO) switch input was out of self-test range — the PCM expected to see the BOO signal transition during the KOER (key-on-engine-running) self-test (brake pressed then released) and didn't see it, or saw it stuck in one state. The BOO signal feeds both cruise control disable and TCC (torque converter clutch) unlock logic, so a stuck BOO will cause shudder under deceleration and refuse to set cruise. Cheapest-first ladder: (1) Press the brake pedal with KOEO and a scan tool watching the BOO PID — should snap from 0V brake-off to ~12V brake-on (or 0V-to-battery-voltage). No transition = bad switch, dragging mechanical pedal-rod, or open harness. (2) Verify brake lights work and pedal feel is normal first — a sticking pedal pad or worn pedal pivot bushing can hold the switch partially actuated ($0 inspection). (3) Adjust or replace the BOO switch — these are $15-30 parts that thread into a bracket above the pedal arm, often field-adjustable to set the actuation point correctly relative to pedal free-play. (4) Check the BOO ground and the 12V feed from the brake-light fuse — a blown brake-light fuse takes out cruise/TCC even though the brake lights are on a separate filament path on some Ford trucks. Expensive-misdiagnosis caveat: P1703 paired with P1701 or P1744 on a 4R70W often points at the same internal trans harness connector contamination as P1701/P1702, not the BOO switch — fluid wicking up the harness can pull the BOO reference into an invalid state at the PCM even though the switch itself is fine; verify the switch transitions cleanly at the switch connector before condemning anything downstream.

Vehicle-specific patterns: 1996-2010 F150/F250 light-duty and 1996-2014 E-series vans with the AODE/4R70W frequently throw P1703 from a worn BOO switch ($22 part) or a sticky pedal-arm bushing causing partial actuation; the Crown Vic Police Interceptor (1996-2011) sees this constantly from the brake-application duty cycle of police use. 1996-2010 Mustang GT/V6 throws P1703 from BOO switch adjustment drift after pedal-pad replacement. 2011-2020 F150 with the 6R80 still uses a BOO switch input but the failure is more often the brake-light switch's secondary contact set (the cruise/TCC contact set is separate from the brake-light contact set on the 6R80 platform). Estimated repair: $25 to $180.