P1702

P1702 is a Ford-specific code meaning the Transmission Range Sensor (TRS, also called MLPS on earlier gearboxes) signal went intermittent — the PCM saw the voltage drop out of all six valid range bands momentarily, then return. This is almost always wiring or connector, not the sensor itself. Cheapest-first ladder: (1) Wiggle-test the trans harness at the TRS connector with KOEO and the scan tool watching live TR voltage — a voltage spike or dropout during wiggle confirms harness/connector fault ($0, 15 min). (2) Pull the TRS connector and inspect for the classic Ford patterns: green corrosion on the pins, fluid wicking from the case-side seal, or backed-out pins from a prior shop disconnecting under load. (3) Voltage-step verification — on the TRS signal wire you should see clean steps at roughly 0.5V (Park), 1.2V (Reverse), 2.0V (Neutral), 2.8V (Drive), 3.6V (2), 4.4V (1); anything outside +/- 0.15V of those targets at the connector is a sensor problem, anything inside spec at the connector but wrong at the PCM is a harness problem. (4) Check the TRS ground reference — a corroded ground stud on the trans bellhousing will float every voltage step upward and set P1702 intermittently as engine bay temperature changes. Expensive-misdiagnosis caveat: don't replace the TRS without first inspecting the trans-case bulkhead seal — fluid migrating through the bulkhead saturates the harness jacket and travels up the wires by capillary action, contaminating the body-side connector; replacing only the sensor leaves the contamination path open and the code returns in 200-500 miles.

Vehicle-specific patterns: AODE/4R70W/4R75W in E-series vans (1996-2014), F150/F250 (1997-2010), Crown Vic Police Interceptor (1996-2011), and Mustang (1996-2010) commonly throws P1702 from a corroded body-side TRS connector after exposure to road salt and trans-cooler line drips — the connector lives at the LH side of the trans case and gets blasted by wheel spray. 2011-2020 F150 and 2011-2017 Mustang/Expedition with the 6R80 see P1702 almost exclusively from the internal lead-frame connector cracking and wicking ATF onto the contacts; Ford's published guidance is lead-frame replacement, not standalone TRS replacement. 1996-2003 Ford Explorer/Mountaineer with the 5R55E throws P1702 from a different but related path — the MLPS lever's internal wiper contacts wear flat at the Park detent and cause dropouts only at standstill. Estimated repair: $45 to $850.