Circuit Description
The vehicle speed sensor (VSS) system is a pulse generator consisting of a speed sensor assembly, located in the case extension, and a toothed vehicle speed sensor reluctor wheel, which is pressed onto the final drive carrier assembly. As the vehicle drives forward, the vehicle speed sensor reluctor wheel rotates. This rotation produces a variable AC signal in the pickup coil that is proportional to vehicle speed. The TCM uses this signal in order to calculate vehicle speed, shift timing and gear ratios.
If the TCM detects a low vehicle speed with a high engine speed while in a drive range, then DTC P0722 sets. DTC P0722 is a type B DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0722 Output Speed Sensor Circuit Low Voltage
Conditions for Running the DTC
| • | No TP sensor DTC P0120 or P0220. |
| • | No ISS DTC P0716 or P0717. |
| • | No OSS DTC P0723. |
| • | Engine speed is greater than 500 RPM for 5 seconds. |
| • | The transmission range is not PARK or NEUTRAL. |
| • | The calc. throttle position is 8 percent or more. |
| • | The engine torque is greater than 50 N·m (37 lb ft). |
| • | The input shaft speed is 1,500-5,000 RPM. |
| • | The TCC slip speed is -20 RPM or more. |
| • | The TFT is -40°C (-40°F) or more. |
Conditions for Setting the DTC
The output shaft speed is 70 RPM or less for 4.5 seconds.
Action Taken When the DTC Sets
| • | The TCM requests the 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 input speed sensor, engine speed and gear ratio for shift timing. |
| • | The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Freeze Frame and Failure Records. |
| • | The TCM stores DTC P0722 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. |
| • | 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.
-
This step tests the ability of the VSS to produce an AC voltage. This step also verifies the integrity of the wiring to the TCM.
-
This step tests the VSS circuit for correct resistance.
Step | Action | Value(s) | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||||||||||
2 |
Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records for reference. Using the Clear Info function will erase the stored Freeze Frame and Failure Records from the TCM. Notice: Support the lower control arms in the normal horizontal position in order to avoid damage to the drive axles. Do not operate the vehicle in gear with the wheels hanging down at full travel. Does the Transmission OSS RPM increase when wheel speed increases? | -- | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 | ||||||||||||
Does the voltage measure greater than the specified value? | 0.4 V AC | Go to Step 8 | Go to Step 4 | |||||||||||||
Is the circuit resistance within the specified range? | 1,650-3,180 ohms | Go to Step 9 | Go to Step 5 | |||||||||||||
5 | Is the circuit resistance greater than the specified value? | 3,180 ohms | Go to Step 11 | Go to Step 6 | ||||||||||||
6 |
Refer to Circuit Testing . Are the signal and ground circuits shorted together? | -- | Go to Step 7 | Go to Step 14 | ||||||||||||
7 | Repair the short between the high signal circuit and the low signal circuit. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 16 | -- | ||||||||||||
8 | Test the high signal circuit of the VSS for a short to ground between the TCM and the VSS. Refer to Testing for Short to Ground and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 15 | ||||||||||||
9 |
Does the DMM display greater than the specified voltage? | 1.0 V | Go to Step 10 | Go to Step 13 | ||||||||||||
10 | Repair the short to voltage in the high signal circuit. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 16 | -- | ||||||||||||
11 | Test the high signal circuit of the VSS for an open between the TCM and the VSS. Refer to Testing for Continuity and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 12 | ||||||||||||
12 | Test the low signal circuit of the VSS for an open between the TCM and the VSS. Refer to Testing for Continuity and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 14 | ||||||||||||
13 |
Refer to Vehicle Speed Sensor Replacement .
Refer to Differential Carrier Inspection . Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 14 | ||||||||||||
14 | Replace the VSS. Refer to Vehicle Speed Sensor Replacement . Did you complete the replacement? | -- | Go to Step 16 | -- | ||||||||||||
15 | Replace the TCM. Refer to Control Module References for replacement, setup and programming. Did you complete the replacement? | -- | Go to Step 16 | -- | ||||||||||||
16 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | Go to Step 17 | Go to Step 2 | ||||||||||||
17 | With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK |
