What does it mean?
P1901 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Turbine Shaft Speed (TSS) Sensor Circuit Intermittent .
Symptoms
- Malfunction indicator lamp on intermittently, often with ratio or slip codes
- Sudden harsh shifts, especially the 1-2 shift, when the signal drops
- Torque converter clutch applying and releasing at the wrong times
- Momentary default (limp) operation that clears after restarting
- Erratic shift points and shift busyness at part throttle
- Symptoms often appear once the transmission is fully warmed up
Likely causes
- Chafed or partially broken wire in the TSS sensor circuit
- Loose, spread or corroded terminal at the transmission case connector
- Fluid wicking into the connector and causing an intermittent contact
- Sensor breaking down when hot and working again when cool
- Debris on the sensor tip or damaged reluctor teeth on the turbine hub
- Incorrect air gap or a loose sensor after previous work
- Faulty input circuit in the transmission control module
How to fix it
- Record freeze frame data to see the temperature and speed when the fault set
- Graph turbine speed alongside engine rpm and output speed during a road test and look for gaps
- Wiggle-test the connector and the harness along the transmission while monitoring the signal
- Inspect the case connector for fluid, corrosion and loose terminals; repair the seal if fluid is present
- Measure sensor resistance or observe its output waveform at operating temperature
- Remove the sensor and inspect the tip and reluctor teeth for debris and damage
- Repair the wiring first, then replace the sensor if the dropouts continue with good circuits