Powertrain Diagnosis

Circuit Description
The Output (Shaft) Speed Sensor (OSS), which is a Permanent Magnet (PM) generator, provides the vehicle speed information to the Powertrain Control Module (PCM). The PM generator produces a pulsing AC voltage as the transmission speed sensors rotor teeth pass through the sensor's magnetic field. The AC voltage level and the number of pulses increase as the speed of the vehicle increases. The PCM then converts the pulsing voltage to a digital signal for vehicle speed. The vehicle speed is used for engine and transmission calculations.

If the PCM detects a low vehicle speed, and there is a high engine speed in a drive gear range, DTC P0723 sets. DTC P0723 is a type D DTC. For California emissions, DTC P0723 is a type B DTC.

Conditions for Running the DTC
^ No TFP manual valve position switch DTC P1810.
^ No Input Shaft Speed (ISS) sensor DTC P0716 or P0717.
^ The engine is running greater than 475 RPM for greater than 7 seconds.
^ System Voltage is 8.0-18.0 volts.
^ No TFP manual valve position switch changes for greater than 16 seconds.
^ No 4WD low switch change within 2 seconds.
^ The OSS RPM is greater than 250 RPM within 2 seconds.
^ The ISS RPM is greater than 700 RPM within 2 seconds.
^ The OSS RPM was greater than 1000 RPM for 2 seconds.
^ No Four Wheel Drive Low DTC.
^ Not in four wheel drive Low.

Conditions for Setting the DTC
The OSS RPM has dropped greater than 1,000 RPM for at least 3.5 seconds.

Action Taken When the DTC Sets
^ For California emissions, the PCM illuminates the Malfunction Indicator Lamp (MIL).
^ The PCM commands maximum line pressure.
^ The PCM freezes the shift adapts.
^ The PCM defaults a calculated output speed value by using the ISS values.
^ The PCM stores DTC P0723 in the PCM history.

Conditions for Clearing the MIL/DTC
^ For Federal and California emissions, the PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
^ A scan tool clears the DTC from PCM history.
^ For Federal and California emissions, the PCM clears the DTC from PCM history if the vehicle completes 40 consecutive warm-up cycles without an emission related diagnostic fault occurring.
^ For vehicles equal to or greater than 15,000 lbs GVW, the PCM clears the DTC from PCM history if the vehicle completes 40 consecutive warm-up cycles without a non-emission related diagnostic fault occurring.
^ The PCM cancels the DTC default actions when the fault no longer exists and the ignition switch is OFF long enough in order to power down the PCM.

Diagnostic Aids
^ DTC P0723 sets when the PCM detects an OSS loss.
^ Inspect the wiring at the PCM, the OSS sensor connector and all other circuit connecting points for the following conditions:
- A backed out terminal
- A damaged terminal
- Reduced terminal tension
- A chafed wire
- A broken wire inside the insulation.
- Moisture intrusion
- Corrosion
^ When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
^ The vehicle may need to be driven to duplicate the intermittent condition.
^ First diagnose and clear any engine DTCs or TP sensor codes. Then inspect for any transmission DTCs that may have reset.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. This step verifies the fault condition.
4. This step verifies the OSS sensor.
7. This step tests the voltage supply to the VSS buffer module.
8. This step tests the integrity of the ground circuit.