Transmission Output Speed Sensor Malfunction?
2 Answers
Due to damage to the automatic transmission input shaft speed sensor, a fault code appears. The following are symptoms of a faulty sensor: 1. Automatic disengagement: During power transmission, the axial force generated by the meshing sliding gears or coupling sleeves exceeds the locking force, causing the gears to automatically shift to neutral. This results from component wear, housing deformation (reducing axial force), insufficient gear meshing length, or failure of the self-locking mechanism (reducing locking force). 2. Gear disarray: Excessive clearance in shift lever components leads to imprecise gear positioning, lever vibration, and difficult shifting. 3. Noise: Causes include excessive gear clearance, impact from housing deformation, bearing failure, insufficient/inappropriate lubricant specification, oil leakage, aged oil seals, housing deformation, or shaft bending.
I saw a similar issue at the repair shop last time. If the transmission output shaft speed sensor malfunctions, the dashboard often flashes warning lights, and the car shifts erratically like it's having a seizure. During repairs, you should first use a diagnostic tool to read the trouble codes—P0720/P0722 are the most obvious indicators. Often, you'll find sludge clogging the sensor pins when you unplug the connector, especially in older cars where the seals have degraded and allowed transmission fluid to seep in. Burnt wiring is also common since high engine bay temperatures can make the wire harness insulation brittle and cause short circuits. When replacing the sensor, pay attention to the gasket's sealing integrity. After installation, you need to drive a few dozen kilometers to let the control unit relearn the speed data, otherwise, the jerking sensation might persist.