P1746

P1746 is a Ford-specific Electronic Pressure Control (EPC) solenoid open-circuit code on the 4R70W / 4R75W / AODE family of 4-speed automatics — the TCM sends a PWM current command to the EPC solenoid in the valve body to vary line pressure (and therefore shift firmness) and looks at the current return on the feedback wire; if it sees zero current flow with the solenoid commanded on, it sets P1746 and forces the transmission into max-pressure limp-home so shifts are harsh but the transmission won't slip or burn clutches. Cheapest-first ladder: (1) Drop the transmission pan, look for metallic debris on the magnet (mild = normal wear; heavy = clutch-pack failure already in progress), and inspect the EPC solenoid for the bullet-shaped boss on the valve body — its connector is the most common failure point because ATF wicks up the wire and corrodes the pin. (2) Ohm the EPC solenoid coil pin-to-pin at the case connector — Ford 4R70W spec is 3-7 ohms cold, anything reading open-circuit means a snapped solenoid lead inside the case or a failed coil. (3) Inspect the case-pass-through connector for ATF intrusion and corrosion — same failure mode as P1700, fixing it often clears P1746 and a stack of associated codes. (4) Back-probe the EPC current at the TCM with the engine running and watch the duty cycle — should sweep cleanly between roughly 30% (firm shifts under load) and 70% (soft shifts at light throttle); flat duty cycle with no current return means a broken feedback circuit, not necessarily a dead solenoid. Don't drop the transmission or rebuild it for a $40 solenoid before reading KAM for prior valve-body swaps and unauthorized tunes — shift-kit installs (TransGo, B&M) on 4R70W frequently re-route or re-pin the EPC circuit and a botched install will read as P1746 even on a healthy transmission.

Vehicle-specific patterns: 1996-2008 Ford F-150 / Crown Vic / Mustang / E-150 with the 4R70W / 4R75W is the canonical P1746 — the case-pass-through connector wicks ATF into the harness and corrodes the EPC pin, or the EPC solenoid coil dies outright around 130-170k miles; either way the fix is pan-down access, solenoid swap, and a Mercon V flush. 1998-2003 Ford Mustang GT / Cobra with the AODE / 4R70W sees P1746 from the same EPC failure pattern, often after track / autocross use that heats the fluid past 250 F. 2003-2011 Crown Vic Police Interceptor and Mercury Marauder see P1746 in fleet/police use where extended idling and high-load pursuit cycles cook the EPC solenoid coil. 1996-2003 E-150/E-250 vans (4R70W) in commercial / shuttle service see P1746 around 200k miles from sheer duty-cycle accumulation on the solenoid. Estimated repair: $180 (EPC solenoid + pan gasket + Mercon V, DIY) to $850 (EPC + case-connector reseal + filter + flush, installed at an AAMCO-level shop).