P0715

P0715 means the TCM isn't getting a valid signal from the Input/Turbine Speed Sensor — the sensor that reads how fast the torque converter's turbine shaft is spinning on its way into the gearset. The TCM compares input shaft RPM against engine RPM to calculate torque converter slip, and against output shaft RPM to calculate actual gear ratio; lose the input signal and the TCM loses its ability to detect slip, manage line pressure, or verify shift completion, so it defaults to limp mode (usually locked in 3rd or 4th with no torque converter lockup). Before pulling any pan, check fluid level and condition first — a low-fluid condition can aerate the pump and produce intermittent speed-sensor signals that look identical to a failed sensor. Then scan live data: with the trans in DRIVE at idle, input shaft RPM should read within 50-100 RPM of engine RPM (converter unlocked, near-stall). At 45 mph cruise with TCC locked, input RPM should equal engine RPM within 20-50 RPM. A reading of 0 or wildly erratic numbers points to the sensor, its wiring (most common), or the reluctor ring inside the case. External sensor and harness are $80-250 to fix; reluctor ring is a teardown.

Vehicle-specific patterns: 2004-2010 Ford F-150/Expedition with the 4R75E/4R70W throws P0715 from a failed input speed sensor at the top of the case (driver's side, accessible without dropping the pan) — these go around 90-130k miles, $40 part, 20-minute fix. 2006-2012 Chrysler 300/Charger/Magnum with the 545RFE/65RFE throws P0715 from the dual input-speed sensors (the 545RFE uses two) when the internal harness connector at the solenoid pack corrodes — a known TSB. 2007-2014 GM trucks with the 6L80/6L90 use input/output speed sensors integrated into the TEHCM (Transmission Electro-Hydraulic Control Module) inside the pan, so P0715 there means dropping the pan and replacing the TEHCM (~$600 part + 2 hours labor). 2009-2015 BMW/Dodge with the ZF 8HP rarely throws P0715 unless the internal mechatronic sleeve has leaked into the wiring — when it does, it's a $1,800-2,800 mechatronic rebuild. Estimated repair: $150 (external sensor swap) to $3,000+ (mechatronic on the 8HP).