P1734

P1734 is a Ford-specific code meaning the MLPS is reporting a voltage consistent with the Manual-2 position (~3.6V on the standard six-step ladder) when the PCM/TCM didn't command or expect 2nd gear — the MLPS is stuck on the M2 step, or the wiper is hanging on the M2 contact during shifts through that position. This is a narrower variant of P1716/P1717 specifically isolating the 2nd-gear manual range. Cheapest-first ladder: (1) Cycle the shifter slowly through all six positions with KOEO and the scan tool watching MLPS voltage — a healthy sensor steps cleanly through 0.5V (P), 1.2V (R), 2.0V (N), 2.8V (D), 3.6V (M2), 4.4V (M1); a sensor stuck on the M2 step will sit at ~3.6V regardless of where the shifter physically is, OR it will hang on 3.6V as you shift past it and only release after a few seconds. (2) Inspect for ATF migration in the MLPS connector — fluid bridging contacts inside the sensor body will create a parasitic short to the M2 contact ($0, 10 min). (3) Verify the shifter cable and manual valve lever are physically reaching all detents — a worn detent spring inside the trans (rooster comb) can let the manual valve hang in M2 even when the driver shifts to Drive, which is a mechanical issue inside the valve body, not the sensor. (4) Confirm the 5V reference and ground at the MLPS are clean — a high-resistance ground will skew every voltage step upward, parking a normally-Drive (2.8V) signal into the M2 (3.6V) band. Expensive-misdiagnosis caveat: P1734 paired with a complaint of 'starts off in 2nd' is often misdiagnosed as MLPS failure when the actual fault is failsafe limp mode — most Ford gearboxes default to 2nd gear in limp mode, and the MLPS code is a downstream symptom; check for solenoid codes (P0750-P0768 family) before chasing the MLPS.

Vehicle-specific patterns: 1996-2003 Ford Explorer/Mountaineer with the 5R55E and 1997-2011 Ford Ranger with the 5R55E throws P1734 from MLPS contact wear at the M2 wiper position — police/fleet Crown Vics see the same wear on the AODE/4R70W. 1996-2010 F150 and 1996-2014 E150/E250/E350 vans with the AODE/4R70W see P1734 from the same wear pattern plus from manual-lever rooster-comb wear inside the trans (a common rebuild item). 1996-2010 Mustang with the AODE/4R70W sees P1734 less often because the shifter sees less M2 use. P1734 specifically on a trans that was recently rebuilt usually points at incorrect MLPS calibration or installation orientation. Estimated repair: $55 to $1,400.