P0721

DTC P0721 Output Speed Sensor (OSS) Circuit Range/Performance





Circuit Description
The vehicle A/T OSS is a magnetic inductive pickup that relays information relative to vehicle speed to the TCM.
Vehicle speed information is used by the TCM to control shift timing, line pressure, and TCC apply and release.
The output speed sensor mounts in the case at the speed sensor rotor, which is pressed onto the spur gear. An air gap of 0.1 mm - 1.3 mm (0.004 - 0.05 inch) is maintained between the sensor and the teeth on the spur gear teeth. The sensor consists of a permanent magnet surrounded by a coil of wire. As the differential rotates, an AC signal induces a higher frequency and voltage measurement at the sensor. Sensor resistance should measure -> at 20°C (68°F). Sensor can measure from 20HZ - 8,000 HZ.

Conditions for Setting the DTC
- Transaxle speed is less than 8,160 rpm.
- The increasing rate of output speed is more than 45,000 rpm/sec.
- System voltage is greater than 8.5 volts.
- Engine is running.
- No engine speed error DTCs P0727, P0725.
- No park/neutral position switch error DTC P0705.
- TCM or ECM is defective.
- Immediately after the above condition occurs.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The TCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Failure Records buffer.
- Adopt Emergency / Substitute mode and constant 4th gear.
- Open lock up clutch.

Conditions for Clearing the MIL/DTC
- The MIL will turn OFF when the malfunction has not occurred after three-ignition cycles.
- A history DTC will clear after 40 consecutive warm up cycles without a fault.
- Using a scan tool can clear history DTCs.

Diagnostic Aids

Steps 1-10:

Steps 11-14:

- When DTC P0721 sets, the possible cause of fault could be OSS (Output speed sensor).