P0723

DIAGNOSTIC TROUBLE CODE (DTC) P0723 AUTOMATIC TRANSMISSION VEHICLE SPEED SENSOR (A/T VSS) INTERMITTENT





Circuit Description
Vehicle speed is provided to the Powertrain Control Module (PCM) by the Automatic Transmission Output (Shaft) Speed Sensor (A/T VSS), which is a Permanent Magnet (PM) generator mounted to the transmission case. The PM generator produces an AC voltage as the speed sensor rotor teeth pass in front of the sensor's magnetic field. The AC voltage level increases as the speed of the vehicle increases. The PCM then converts the AC voltage into a digital signal. The PCM uses the vehicle speed to determine shift timing, Torque Converter Clutch (TCC) apply, TCC release, and gear ratio calculations.
When the PCM detects an unrealistic large change in vehicle speed, then Diagnostic Trouble Code (DTC) P0723 sets.

Conditions For Setting The DTC
- Engine running.
- No Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.) DTC P1810.
- Time since last manual gear select lever change is greater than 3 seconds.
- A decrease in output speed greater than 900 rpm in park or neutral or a decrease greater than 1300 rpm in drive.

Action Taken When The DTC Sets
- PCM will illuminate the Malfunction Indicator Lamp (MIL) after two consecutive trips with a failure reported.
- PCM freezes shift adapts from being updated.
- PCM commands maximum line pressure.
- The PCM calculates output speed based on input speed, engine speed, and commanded gear.
- DTC P0723 will be stored in PCM memory.

Conditions For Clearing The DTC
- The PCM will turn the MIL off after the output speed sensor has not failed this DTC for three consecutive ignition cycles.
- History DTCs can be cleared by using a Scan Tool.

Diagnostic Aids
- Condition may be intermittent. Check for loose Vehicle Speed Sensor (VSS) mounting or poor sensor connection.
- Inspect for a damaged VSS or transmission rotor teeth.
- Inspect the wiring for poor electrical connections at the PCM and at the A/T VSS. Look for possible bent, backed out, deformed or damaged terminals. Check for weak terminal tension as well. Also check for chafed wires that could short to bare metal or other wiring. Inspect for broken wire inside the insulation.
- If diagnosing for a possible intermittent short or open condition, move or massage the wiring harness while observing test equipment for a change.

Chart Test Description
The numbers below refer to the numbered steps on the diagnostic chart.
3. This test checks the A/T VSS for correct resistance.
4. This tests the A/T VSS ability to produce an AC current and the integrity of the wiring to the PCM.





DTC P0723 - Automatic Transmission Vehicle Speed Sensor (A/T VSS) Intermittent