5L40-E / 5L50-E Automatic Transmission
DTC P0723
Circuit Description
The output speed sensor (OSS) assembly provides vehicle speed information to the transmission control module (TCM). The OSS assembly is a permanent magnet generator. The sensor is mounted in the transmission case facing the rear internal gear which is splined to the output shaft assembly. As the output shaft and internal gear rotate, the toothed rotor of the internal gear produces AC voltage as the rotor teeth pass through the magnetic field of the sensor. The AC voltage level and the number of pulses increase as the speed of the vehicle increases. The TCM converts the voltage to vehicle speed. The TCM uses the output shaft speed signal to determine shift timing and torque converter clutch (TCC) scheduling.
If the TCM detects an unrealistic drop in output shaft speed, DTC P0723 sets. DTC P0723 is a type B DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0723 Output Speed Sensor Circuit Intermittent
Conditions for Running the DTC
^ No 1-2 Shift Solenoid Electrical DTC P0974.
^ No ISS DTCs P0716 or P0717.
^ No IMS DTCs P1815, P1820, P1822, P1823, P1825 or P1826.
^ The engine run time is greater than 5 seconds.
^ The transmission is not in PARK or NEUTRAL.
^ The transmission output speed is greater than 1,400 RPM for 2 seconds or greater.
^ One of the following conditions exist:
- The transmission input shaft speed has not decreased for at least 2 seconds.
- The transmission output shaft speed has not increased greater than 500 RPM for at least 2 seconds.
Conditions for Setting the DTC
The transmission output shaft speed drops greater than 1,300 RPM for at least 3 seconds.
Action Taken When the DTC Sets
^ The TCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
^ The TCM commands maximum line pressure.
^ The TCM freezes transmission adaptive functions.
^ The TCM calculates vehicle speed from the automatic transmission input shaft speed sensor and commanded gear.
^ The TCM inhibits autograde braking.
^ At the time of the first failure, the TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as a Failure Record.
^ At the time of the second failure, the ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as a Freeze Frame.
^ The TCM stores DTC P0723 in TCM history.
Conditions for Clearing the MIL/DTC
^ The ECM turns OFF the MIL after the sixth consecutive drive trip in which the TCM does not send a MIL illumination request.
^ A scan tool can clear the MIL/DTC.
^ The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without an emission related diagnostic fault occurring.
^ The TCM cancels the default actions when the ignition is OFF long enough in order to power down the TCM.
Diagnostic Aids
Ensure the OSS sensor is properly torqued to the transmission housing.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
3. The resistance measurement will not change if either the OSS high signal circuit or the OSS low signal circuit, but not both, is shorted to ground. The vehicle speed detector in the TCM and the OSS are matched in such a way that an open or a short to ground in the OSS low signal circuit will not usually cause a loss of speed signal or a DTC P0723 to set.
6. This step isolates the short between the OSS and the wiring.
8. The DMM will detect AC voltage if the OSS high signal circuit is shorted to ground.
11. Refer to the latest procedures for TCM reprogramming.
