Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Output Shaft Speed Sensor
The Output Shaft Speed (OSS) Sensor is a magnetic inductive pickup that relays information relative to vehicle speed to the Powertrain Control Module (PCM). Vehicle speed information is used by the PCM to control shift timing, line pressure, and TCC apply and release. The OSS sensor mounts in the case at the speed sensor rotor which is pressed onto the differential. See Figure or Figure . An air gap of 0.011-0.062" (0.27-1.57 mm) is maintained between the sensor and the teeth on the speed sensor rotor. The sensor consists of a permanent magnet surrounded by a coil of wire. As the differential rotates, an AC signal is induced in the OSS sensor. Higher vehicle speeds induce a higher frequency and voltage measurement at the sensor. Sensor resistance should be 1500-1650 ohms when measured at 68°F (20°C). Output voltage will vary with speed from a minimum of 0.5 volts AC at 25 RPM to 200 volts AC at 1728 RPM.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.