P0723
DTC P0723
Circuit Description
The vehicle speed sensor (VSS) is a permanent magnet generator attached to the transmission case. The final drive assembly has a toothed wheel, VSS rotor. As the final drive assembly rotates, an AC voltage is induced and transmitted to the transmission control module (TCM). The TCM converts the AC voltage into a digital signal. The TCM uses vehicle speed to determine shift timing, torque converter clutch apply and release and gear ratio.
If the TCM detects a loss of vehicle speed while the vehicle is in motion, then 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 MAF DTCs P0101, P0102 or P0103.
* No MAP DTCs P0106, P0107 or P0108.
* No TP DTCs P0121, P0122 or P0123.
* No VSS DTC P0722.
* No AT ISS DTCs P0716 or P0717.
* The engine run time is greater than 5 seconds.
* The time since the gear select lever change is greater than 6 seconds.
* The transmission input shaft speed has not changed by 500 RPM or greater for at least 2 seconds.
* LD8: The transmission output shaft speed is 1,000 RPM or greater for 2 seconds.
* L37: The transmission output shaft speed is 1,193 RPM or greater for 2 seconds.
Conditions for Setting the DTC
* LD8: The transmission output shaft speed drops 1,200 RPM or greater for at least 3.25 seconds.
* L37: The transmission output shaft speed drops 1,431 RPM or greater for at least 3.25 seconds.
Action Taken When the DTC Sets
* The TCM requests the engine control module (ECM) to illuminate 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 ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as Freeze Frame and Failure Records and the TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Failure Records.
* The TCM stores DTC P0723 in TCM history during the second consecutive trip in which the Conditions for Setting the DTC are met.
Conditions for Clearing the MIL/DTC
* The ECM turns OFF the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request.
* The TCM clears the DIC message when the condition no longer exists.
* 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 DTC default actions when the ignition switch is OFF long enough in order to power down the TCM.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. This step tests for DTCs and for a vehicle speed signal. It is important to record Freeze Frame and Failure Record information before proceeding further.
5. This step tests for a resistance value greater than 1,911 ohms which would indicate an open in the high signal circuit, the low signal circuit or the VSS.
