DTC P0722 Output Speed Sensor Circuit Low Input Diesel Only
Circuit Description
The speed sensor circuit consists of a magnetic induction type sensor, which is the Output Shaft Speed (OSS) Sensor, a Vehicle Speed Sensor (VSS) Buffer Module, and wiring. Gear teeth pressed onto the output shaft carrier assembly induce an alternating voltage into the sensor. This signal transmits to the VSS Buffer Module. The VSS Buffer Module compensates for various final drive ratios. The VSS Buffer Module also converts the AC OSS Sensor signal into a 40 pulse per revolution (PPR) DC 5 volt square wave form signal on circuit 437 to indicate transmission output speed.
When the Powertrain Control Module (PCM) detects a low output speed when the vehicle has a high engine speed in a drive gear range, then DTC P0722 sets. DTC P0722 is a type B DTC.
Conditions for Setting the DTC
| • | No TFP Val. Position Sw. DTC P1810. |
| • | The APP Angle is greater than 12%. |
| • | The engine torque must be 100-565 N·m (80-450 lb ft). |
| • | The engine speed must be 2000-3800 RPM. |
| • | The A/T ISS Sensor speed is greater than 2000 RPM. |
| • | The transmission is not in Park or Neutral. |
| • | The engine vacuum is 0-105 kPa. |
| • | The OSS Sensor speed is less than 200 RPM for at least 3 seconds. |
Action Taken When the DTC Sets
| • | The PCM defaults to maximum line pressure. |
| • | The PCM freezes shift adapts. |
| • | The PCM defaults to the calculated output speed value using the Input Shaft Speed Sensor values. |
Conditions for Clearing the DTC
- The PCM turns OFF the MIL after three consecutive ignition cycles without a failure reported.
- A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported.
- The PCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the PCM.
Diagnostic Aids
| • | Inspect the wiring for poor electrical connections at the PCM. Inspect the wiring for poor electrical connections at the transmission 20-way connector. Look for the following problems: |
| - | A bent terminal |
| - | A backed out terminal |
| - | A damaged terminal |
| - | Poor terminal tension |
| - | A chafed wire |
| - | A broken wire inside the insulation |
| • | When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change. It may be necessary to drive the vehicle. |
| • | Inspect the Speed Sensor wiring for contact with sharp metal edges. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step verifies the fault condition.
-
This step tests OSS Sensor integrity.
-
This step verifies power and ground to the VSS Buffer Module.
-
This step verifies the PCM input controlled by the Speed Buffer.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||||||
Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data. Does the Transmission OSS increase with the drive wheel speed? | -- | Cannot verify fault. Exit DTC table and go to Diagnostic Aids | ||||||
Is the voltage greater than the specified value? | Greater than 0.5 volts at above 10 mph. | |||||||
4 |
Is the voltage greater than the specified value? | 0.5 volts AC | ||||||
5 |
Refer to Electrical Diagnosis, Section 8. Did you find a problem? | -- | ||||||
6 |
Refer to Electrical Diagnosis, Section 8. Did you find a problem? | -- | -- | |||||
7 |
Is the voltage greater than the specified value? | 10.5 volts DC | ||||||
8 | Inspect the ignition feed circuit 39 for an open. Did you find and correct a problem? | -- | -- | |||||
With the key to the ON position, measure the voltage between terminals 8 and 9 of the VSS Buffer connector. Is the voltage greater than the specified value? | 10.5 volts DC | |||||||
10 | Inspect the VSS Buffer Module ground circuit 451 for an open. Was the problem found and corrected? | -- | -- | |||||
11 | With the connector OFF of the VSS Buffer Module and the key to the ON position, measure the voltage between terminal 13 of the VSS Buffer Harness Connector and a good ground. Is the voltage within the specified value? | 4.8-5.2 volts DC | ||||||
12 | Is the voltage in Step 12 greater than the specified voltage? | 5.2 volts DC | ||||||
13 | Inspect circuit 437 for an open or short to ground. Did you find a problem? | -- | ||||||
14 | Inspect circuit 437 for a short to power. Did you find a problem? | -- | ||||||
15 |
Is the voltage within the specified values? | 1.5-3.5 volts DC | ||||||
16 |
Refer to Repair Procedures, Section 8. Did you correct the problem? | -- | -- | |||||
17 | Inspect the PCM for faulty or intermittent connections. Did you find a problem? | -- | ||||||
18 | Replace the OSS Sensor. Is the replacement complete? | -- | -- | |||||
19 | Replace the VSS Buffer Module. Is the replacement complete? | -- | -- | |||||
20 | Replace the PCM. Is the replacement complete? | -- | -- | |||||
21 | In order to verify your repair, perform the following procedure:
Has the test run and passed? | -- | System OK |
