GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Saturn 🢒 2004 🢒 ION 🢒 Transmission/Transaxle 🢒 Automatic Transmission - VT25-E 🢒 DTC P0723

Object Number: 882390 Size: MF
Master Electrical Component List
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice

Circuit Description

The output shaft speed (OSS) sensor provides vehicle speed information to the transmission control module (TCM). The OSS is a permanent magnet generator. The OSS sensor is mounted inside the transmission, under the control valve body cover. The sensor faces the output shaft speed sensor reluctor ring. As the reluctor ring rotates, an AC voltage is induced and transmitted to the transmission control module (TCM). The AC voltage level and the number of pulses increase as the speed of the vehicle increases. The TCM converts the AC voltage to vehicle speed. The TCM uses the output speed signal to help determine line pressure, transmission ratio control patterns and TCC apply pressure and timing.

If the TCM detects an unrealistic drop in output shaft speed, DTC P0723 sets. DTC P0723 is a type A DTC.

Conditions for Running the DTC
    • No transmission range switch DTCs P0705, P1756, or P1758.
    • No ISS DTCs P0716 or P0717.
    • The engine speed is greater than 500 RPM for 5 seconds.
    • The selected range is not PARK or NEUTRAL.
    • The time since the gear select lever change is greater than 6 seconds.
    • The transmission input shaft speed is greater than 200 RPM.
    • The transmission output shaft speed is 600 RPM or greater for 5 seconds.
    • The transmission output shaft speed changes 200 RPM or less every 0.25 seconds for 3 seconds.
    • The transmission input shaft speed changes 100 RPM or less every 0.25 seconds for 3 seconds.

Conditions for Setting the DTC

The transmission output shaft speed drops 500 RPM or greater and then remains for at least 0.8 seconds.

Action Taken When the DTC Sets
    • The TCM requests the ECM to illuminate the malfunction indicator lamp (MIL).
    • The TCM moves the speed ratio towards a target ratio and then freezes ratio changes.
    • The TCM discontinues use of the closed loop ratio control algorithm. This causes the speed ratio to be defaulted and possibly not accurate. The resulting open loop control may or may not provide optimum ratio performance.
    • The TCM calculates output shaft speed from the input shaft speed sensor and the commanded speed ratio.
    • The TCM commands a line pressure increase for all operating conditions.
    • The TCM freezes main line pressure transmission adaptive functions.
    • 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.
    • The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM records this information as Failure Records.
    • The TCM stores DTC P0723 in TCM history.

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.
    • 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.

Diagnostic Aids
    • Ensure the OSS sensor is properly installed in the transmission.
    • Inspect the connectors at the TCM, the transmission, and all other circuit connecting points for an intermittent condition. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
    • Inspect the circuit wiring for an intermittent condition. Refer to Testing for Electrical Intermittents in Wiring Systems.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. 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.

    2.

  2. This step isolates the short between the OSS and the wiring.

    3.

  3. Refer to the latest procedures for TCM reprogramming.

Step

Action

Values

Yes

No

1

Did you perform the Diagnostic System Check - Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls in Engine Controls - 2.2L (L61)

2

Notice: In order to avoid damage to the drive axles, support the lower control arms in the normal horizontal position. Do not run the vehicle in gear with the wheels hanging down at full travel.

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.

    3. Important: 

       • Before clearing the DTC, use the scan tool in order to record the ECM Freeze Frame and the TCM Failure Records. Using the Clear Eng./Trans. DTC Info function erases the Freeze Frame and Failure Records from the ECM and the TCM.
       • Using the Clear Eng./Trans. DTC Info function erases stored DTCs in both the ECM and TCM.

  3. Record the DTC Freeze Frame and Failure Records.
  4. Clear the DTC.
  5. Raise the drive wheels.
  6. Support the lower control arms so that the drive axles are in a horizontal, straight, position.
  7. Start the engine.
  8. Shift the transmission into D.
  9. Select Transmission OSS on the scan tool.

Does the scan tool display transmission output speed above the specified value?

200 RPM

Go to Intermittent Conditions in Engine Controls - 2.2L (L61)

Go to Step 3

3
  1. Turn OFF the ignition.
  2. Disconnect the TCM.
  3. Measure the resistance between the OSS high signal and the OSS low signal circuits at the TCM connector.

Is the resistance within the specified range?

1,000-2,000 ohms

Go to Step 5

Go to Step 4

4

Test the OSS high signal circuit and the OSS low signal circuit for the following conditions:

    • An open circuit or high resistance condition
    • OSS high signal and OSS low signal circuits shorted together

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct a condition?

--

Go to Step 13

Go to Step 9

5

Measure the resistance between the OSS high signal circuit at the TCM connector and ground.

Is the resistance greater than the specified value?

50K ohms

Go to Step 8

Go to Step 6

6
  1. Leave the DMM connected between the OSS high signal circuit and ground.
  2. Disconnect the AT inline 20-way connector.
  3. Measure the resistance.

Is the resistance greater than the specified value?

50K ohms

Go to Step 9

Go to Step 7

7

Repair the short to ground in the OSS high signal circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 13

--

8
  1. Connect the DMM between the OSS high signal and the OSS low signal circuits at the TCM 64-way connector.
  2. Measure the AC voltage with the DMM while rotating the drive wheels by hand.

Is the AC voltage equal to or greater than the specified value?

0.5 V

Go to Step 9

Go to Step 10

9

Test for continuity between the OSS high signal circuit of the TCM C2 64-way connector and all other terminals except the OSS low signal circuit.

Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.

Did you find and correct a condition?

--

Go to Step 13

Go to Step 12

10
  1. Remove the OSS. Refer to Input and Output Speed Sensor Replacement .
  2. Inspect the OSS and the OSS rotor for the following conditions:
    3. • Poor connections at leadframe
    • OSS damage
    • OSS reluctor damage
    • Excessive air gap between the OSS reluctor and the OSS
    • Incorrect alignment between the OSS and the OSS reluctor
  3. Repair or replace any of the above items as necessary.

Did you find and correct a condition?

--

Go to Step 13

Go to Step 11

11

Replace the OSS. Refer to Input and Output Speed Sensor Replacement .

Did you complete the repair?

--

Go to Step 13

--

12

Replace the TCM. Refer to Transmission Control Module Replacement .

Did you complete the replacement?

--

Go to Step 13

--

13

Perform the following procedure in order to verify the repair:

  1. Select DTC.
  2. Select Clear Info.
  3. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text and observe Transmission OSS on the scan tool.
  4. Ensure the Transmission OSS is greater than 350 RPM and does not drop greater than 300 RPM for 5 seconds.
  5. Select Specific DTC.
  6. Enter DTC P0723.

Has the test run and passed?

--

Go to Step 14

Go to Step 2

14

With the scan tool, observe the stored information, capture info and DTC info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List in Engine Controls - 2.2L (L61)

System OK