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P0715Cars & SUVs
Moderate

P0715Input or turbine shaft speed sensor circuit malfunction

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Check soon

— The transmission protects itself with default strategies, but repeated harsh shifts wear clutches quickly — schedule the repair rather than living with it.

What does this severity mean?

General guidance only — not a substitute for a professional inspection or official roadside / out-of-service criteria (e.g. CVSA OOSC) in your jurisdiction.

Part of system: Transmission control & ratio monitoring

Reports that the input or turbine shaft speed signal is missing or implausible, which matters because the controller uses the ratio between input and output speed to judge when a shift completed and whether the converter is locked. Without it, shift quality collapses into harsh engagements, flare between gears, or a limp default gear. Test the circuit before dropping the pan: back-probe supply and ground, then scope the signal while a helper drives so you can see whether pulses disappear at a specific road speed or fluid temperature. Magnetic sensors collect steel filings on the tip, and heavy fuzz there is also a clue that something inside is wearing. Inspect the harness where the loom crosses the case, and confirm the connector is not wet with fluid wicking up from a leaking seal.

Parts that may be involved

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Vehicles often affected

Common on transmissions where the sensor sits in the case near the bellhousing, and on units that have already shed clutch material into the fluid.

Typical symptoms

  • Harsh engagements or shift flare between gears
  • Transmission dropping into a default gear
  • Speedometer working normally but shift quality poor
  • Shift points wandering with no repeatable pattern
  • Input speed PID reading zero while the vehicle moves

Likely causes

  • Speed sensor failed or loaded with steel filings on the tip
  • Harness chafed where the loom crosses the transmission case
  • Case connector wet with fluid wicking up the wires
  • Reluctor teeth damaged or the rotor loose on the shaft
  • Internal wear producing debris that also disturbs the signal

Recommended checks

  1. 1

    Back-probe supply and ground, then scope the signal while driving

  2. 2

    Remove the sensor and inspect the tip for metal fuzz

  3. 3

    Compare input and output speed PIDs through a full shift

  4. 4

    Repair chafed wiring and reseal the case connector

  5. 5

    Investigate internal wear if debris keeps coming back

DIY vs professional

DIY: external sensor replacement where accessible and connector work. Pro: in-pan sensors, waveform diagnosis, internal inspection.

See also

Related terms

Content reviewed by a heavy-duty technician. About our editorial approach