P0721

P0721-OUTPUT SPEED SENSOR CIRCUIT PERFORMANCE





For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

The transmission system uses two speed sensors. One is used to measure input rpm (primary pulley) and one to measure output rpm (secondary pulley).

The Input Speed sensor detects the primary pulley rpm by the use of a three-wire magnetic pickup device that generates a square wave signal as rotation occurs and is monitored by the Transmission Control Module (TCM). These inputs are essential for proper transmission operation.

- When Monitored:
Ignition on, engine running with the transmission in a valid forward gear.

System voltage between 9.0 and 16.0 volts

Vehicle speed greater than 10 Km/h (6 mph).

Accelerator Pedal Position (APP) greater than 12.5%.

Engine rpm greater than 450 rpm with TCC lock-up enabled.

No DTCs from the following:

- TCC Solenoid
- Lock-up solenoid
- Step motor
- Input or Output Speed Sensor No Signal
- Transmission Range Sensor (TRS)
- Sensor Ground
- CAN

All the below conditions must be present for the period of 5 seconds for the DTC to set:

- Set Condition:

- Engine speed minus the primary speed is greater than 1000 rpm.
- Secondary speed multiplied by the estimated ratio, minus the Primary speed is greater than 1000 rpm.
- Engine speed minus the Secondary speed, multiplied by the estimated ratio is less than 1000 rpm.






Always perform the CVT Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview

1. CHECK TO SEE IF THE DTC IS ACTIVE
1. With the scan tool, read Transmission DTCs.

Is the status Active or is the Starts Since Set counter 2 or less for this DTC?

Yes

- Go To 2

No

- Go To 11

2. CHECK FOR ENGINE CAM OR CRANK SENSOR DTCs
1. With the scan tool, check engine DTCs.

Are there any Engine Cam or Crank sensor DTCs present?

Yes

- Refer to DTC Based Diagnostics and perform the appropriate diagnostic procedure.
- Perform CVT TRANSMISSION VERIFICATION TEST. CVT Transmission Verification Test

No

- Go To 3

3. CHECK THE (T16) TRANSMISSION CONTROL OUTPUT CIRCUIT FOR AN OPEN (HIGH RESISTANCE)




1. Disconnect the Output Speed Sensor harness connector.
2. Ignition on, engine not running
3. With the scan tool under TIPM, actuate the Transmission.
4. Using a 12-volt test light connected to ground, check the (T16) Transmission Control Output circuit at the Output Speed Sensor harness connector.

NOTE: The test light must illuminate brightly. Compare the brightness to that of a direct connection to the battery.

Does the test light illuminate brightly?

Yes

- Go To 4

No

- Repair the (T16) Transmission Control Output circuit for an open or high resistance.
- Perform CVT TRANSMISSION VERIFICATION TEST. CVT Transmission Verification Test

4. CHECK THE (T52) OUTPUT SPEED SENSOR SIGNAL CIRCUIT




1. With the scan tool under TIPM, stop the Transmission actuator.
2. Turn the ignition off, wait 5 seconds, then turn the ignition on.
3. Measure the voltage of the (T52) Output Speed Sensor Signal circuit.

Pick the answer that best matches your findings:

Voltage above 9.0 volts

- Go To 5

Voltage below 9.0 volts

- Go To 6

5. CHECK THE (T52) OUTPUT SPEED SENSOR SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE




1. Turn the ignition off to the lock position.
2. Disconnect the TCM C2 harness connector.
3. Ignition on, engine not running
4. Measure the voltage of the (T52) Output Speed Sensor Signal circuit.

Is the voltage above 0.2 volts?

Yes

- Repair the (T52) Output Speed Sensor Signal circuit for a short to voltage.
- Perform CVT TRANSMISSION VERIFICATION TEST. CVT Transmission Verification Test

No

- Using the schematics as a guide, check the Transmission Control Module (TCM) terminals for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. Check for any Service Bulletins for possible causes that may apply. If no problems are found, replace the TCM.
- Perform CVT TRANSMISSION VERIFICATION TEST. CVT Transmission Verification Test

6. CHECK THE (T52) OUTPUT SPEED SENSOR SIGNAL CIRCUIT FOR AN OPEN (HIGH RESISTANCE)




1. Turn the ignition off to the lock position.
2. Disconnect the TCM C2 harness connector.
3. Connect a jumper wire between the (T52) Output Speed Sensor Signal circuit and B(+) in the Output Speed Sensor harness connector.
4. Using a 12-volt test light connected to ground, check the (T52) Output Speed Sensor Signal circuit in the TCM C2 harness connector.

NOTE: The test light must illuminate brightly. Compare the brightness to that of a direct connection to the battery.

Does the test light illuminate brightly?

Yes

- Go To 7

No

- Repair the (T52) Output Speed Sensor Signal circuit for an open or high resistance.
- Perform CVT TRANSMISSION VERIFICATION TEST. CVT Transmission Verification Test

7. CHECK THE (T130) OUTPUT SPEED SENSOR GROUND CIRCUIT SHORT TO VOLTAGE




1. Turn the ignition off to the lock position.
2. Disconnect the jumper wire.
3. Disconnect the TCM C2 harness connector.
4. Ignition on, engine not running
5. Measure the voltage of the (T130) Output Speed Sensor Ground circuit.

Is the voltage above 0.2 volts?

Yes

- Repair the (T130) Output Speed Sensor Ground circuit for a short to voltage
- Perform CVT TRANSMISSION VERIFICATION TEST. CVT Transmission Verification Test

No

- Go To 8

8. CHECK THE (T130) OUTPUT SPEED SENSOR GROUND CIRCUIT FOR AN OPEN (HIGH RESISTANCE)




1. Turn the ignition off to the lock position.
2. Connect a jumper wire between the (T130) Output Speed Sensor Ground circuit in the Output Speed Sensor harness connector and B(+).
3. Using a 12-volt test light connected to ground, check the (T130) Output Speed Sensor Ground circuit in the TCM C2 harness connector.

Does the test light illuminate brightly?

Yes

- Go To 9

No

- Repair the (T130) Output Speed Sensor Ground circuit for an open or high resistance.
- Perform CVT TRANSMISSION VERIFICATION TEST. CVT Transmission Verification Test

9. CHECK THE OUTPUT SPEED SENSOR
1. Turn the ignition off to the lock position.
2. Remove the Output Speed Sensor.
3. Check the Output Speed Sensor for any debris buildup or damage.

Did the Output Speed Sensor show any signs of debris buildup or damage?

Yes

- If there is a debris build up, clean the Output Speed Sensor as necessary and reinstall. If damaged or questionable in condition, replace the Output Speed Sensor.
- Perform CVT TRANSMISSION VERIFICATION TEST. CVT Transmission Verification Test

No

- Go To 10

10. REPLACE SPEED SENSOR AND TEST DRIVE VEHICLE
1. Turn the ignition off to the lock position.
2. Replace the Output Speed Sensor
3. Reconnect all previously disconnected harness connectors.
4. Ignition on, engine not running
5. With the scan tool, erase all Transmission DTCs.
6. Perform CVT TRANSMISSION VERIFICATION TEST. CVT Transmission Verification Test

NOTE: Test drive the vehicle to speeds that will allow Torque Converter lock-up.

7. With the scan tool, read Transmission DTCs.

Does the DTC P0721 reset?

Yes

- Using the schematics as a guide, check the Transmission Control Module (TCM) terminals for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. Check for any Service Bulletins for possible causes that may apply. If no problems are found, replace the TCM.
- Perform CVT TRANSMISSION VERIFICATION TEST. CVT Transmission Verification Test

No

- Test Complete.

11. CHECK THE WIRING AND CONNECTORS
1. The conditions necessary to set this DTC are not present at this time.
2. Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
3. Wiggle the wires while checking for shorted and open circuits.

Were there any problems found?

Yes

- Repair as necessary.
- Perform CVT TRANSMISSION VERIFICATION TEST. CVT Transmission Verification Test

No

- Test Complete.