ISS/OSSSensor

Input and Output Shaft Speed Sensors (ISS/OSS)

Group: Transmission

The ISS and OSS sensors measure the speed of the automatic transmission input and output shafts. By comparing them, the computer calculates the real gear ratio and detects a slipping clutch.

Contents

What does the ISS/OSS sensor do?

The ISS (or turbine speed sensor) measures how fast the torque converter output is turning; the OSS measures the speed of the shaft that drives the wheels. Dividing one by the other, the computer knows which gear is really engaged. If the ratio does not match the commanded gear, it logs incorrect ratio codes (P0730 to P0736) or torque converter slip codes (P0740 to P0744).

Where is it located?

In the automatic transmission case, bolted in and pointing at toothed wheels or drums.

Signal type and reference values

  • Inductive (2 wires, AC voltage) or Hall (3 wires, square wave).
  • The frequency rises with shaft speed.

Values are a guide only: always check the manufacturer's data for your vehicle.

Symptoms of a bad ISS/OSS sensor

  • Harsh, late or erratic shifts.
  • The transmission does not shift or goes into limp mode (usually 2nd or 3rd gear).
  • Wrong speedometer reading if the OSS supplies the vehicle speed.
  • Codes P0715 to P0723 and P0730.

How to test the ISS/OSS sensor step by step

  1. With the scan tool, compare input, output and engine RPM in each gear.
  2. Check that the tip of each sensor is clean: metal particles from the transmission stick to the magnet.
  3. Measure resistance (inductive) or supply and ground (Hall).
  4. If the sensors are good and the ratio is wrong, the problem is mechanical or hydraulic (clutches, solenoids, fluid).

Trouble codes related to the ISS/OSS sensor

Frequently asked questions about the ISS/OSS sensor

Can a P0730 be just a sensor?
It can, but it is more often low or degraded fluid, a solenoid or worn clutches. Check the fluid and the sensors first.
What is the difference between the turbine speed sensor and the ISS?
They are the same sensor; the name depends on the manufacturer.

Updated September 25, 2026. Values are a guide only: always confirm them in the service manual for your engine.

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