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P1720






P1720-LOSS OF OUTPUT SPEED / WHEEL SPEED





For a complete wiring diagram refer to Diagrams/Electrical. Electrical Diagrams


Theory of Operation


The Output Speed sensor is used to determine gear position by applying the signal to a static shift schedule map. The Output Speed sensor is also used together with Input Speed sensor to calculate gear ratios. The TCM compares Output shaft speed to Vehicle speed buss messages to diagnosis the system. If the TCM detects a fault with the Output speed signal, it switches to vehicle speed to determine gear position.



When Monitored:
- Output speed is greater than 807 rpm and the PRNDL is not in Park or Neutral.
- Input Speed sensor is reporting as failed or CAN wheel speed not available.

Set Condition:
- If Output speed is greater than 3227 rpm and the TCM detects a decrease of Output speed greater than 141 rpm in 5 ms.
- If Output speed is greater than 2017 rpm and the TCM detects a decrease of Output speed greater than 202 rpm in 5 ms.
- If Output speed is greater than 807 rpm and the TCM detects a decrease of Output speed greater than 303 rpm in 5 ms.







Always perform the AS68RC Pre-Diagnostic Troubleshooting procedure before proceeding. AS68RC Pre-Diagnostic Troubleshooting Procedure



Diagnostic Test


1. CHECK IF THE DTC IS CURRENT

Ignition on, engine not running.

With the scan tool, read Engine DTCs.

Record the Freeze Frame data for the reported DTC.

With the scan tool, erase DTCs.

Turn the ignition off to the lock position.

Using the Freeze Frame data recorded earlier, try to duplicate the conditions in which the DTC originally set.


NOTE: It may be necessary to road test the vehicle to duplicate the original set conditions.

With the scan tool, read Engine DTCs.

Did the DTC reset?

Yes

- Go To 2

No

- Go To 10



2. CHECK THE (T14) OUTPUT SPEED SENSOR SIGNAL CIRCUIT FOR AN OPEN





Turn the ignition off to the lock position.

Disconnect the TCM C2 harness connector.

Disconnect the Output Speed Sensor harness connector.

Measure the resistance of the (T14) Output Speed Sensor Signal circuit between the TCM C2 harness connector and the Output Speed Sensor harness connector.

Is the resistance below 5.0 ohms?

Yes

- Go To 3

No

- Repair the (T14) Output Speed Sensor Signal circuit for an open.
- Perform AS68RC VERIFICATION TEST. AS68RC Transmission Verification Test



3. CHECK THE (T72) SENSOR GROUND CIRCUIT FOR AN OPEN





Measure the resistance of the (T72) Sensor Ground circuit between the TCM C2 harness connector and the Output Speed Sensor harness connector.

Is the resistance below 5.0 ohms?

Yes

- Go To 4

No

- Repair the (T72) Sensor Ground circuit for an open.
- Perform AS68RC VERIFICATION TEST. AS68RC Transmission Verification Test



4. CHECK THE (T14) OUTPUT SPEED SENSOR SIGNAL CIRCUIT FOR A SHORT TO GROUND





Measure the resistance between ground and the (T14) Output Speed Sensor Signal circuit.

Is the resistance below 100k ohms?

Yes

- Repair the (T14) Output Speed Sensor Signal circuit for a short to ground.
- Perform AS68RC VERIFICATION TEST. AS68RC Transmission Verification Test

No

- Go To 5



5. CHECK THE (T14) OUTPUT SPEED SENSOR SIGNAL CIRCUIT FOR A SHORT TO ANOTHER CIRCUIT





Measure the resistance between the (T14) Output Speed Sensor Signal circuit and all other circuits in the TCM C2 harness connector.

Is the resistance below 100k ohms between the (T14) Output Speed Sensor Signal circuit and any other circuit(s) in the TCM C2 harness connector?

Yes

- Repair the (T14) Output Speed Sensor Signal circuit for a short to another circuit(s).
- Perform AS68RC VERIFICATION TEST. AS68RC Transmission Verification Test

No

- Go To 6



6. CHECK THE (T72) SENSOR GROUND CIRCUIT FOR A SHORT TO ANOTHER CIRCUIT





Measure the resistance between the (T72) Sensor Ground circuit and all other circuits in the TCM C2 harness connector.

Is the resistance below 100k ohms?

Yes

- Repair the (T72) Sensor Ground circuit for a short to another circuit(s).
- Perform AS68RC VERIFICATION TEST. AS68RC Transmission Verification Test

No

- Go To 7



7. CHECK THE (T14) OUTPUT SPEED SENSOR SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE





Ignition on, engine not running.

Measure the voltage of the (T14) Output Speed Sensor Signal circuit in the Output Speed Sensor harness connector.

Is there any voltage present?

Yes

- Repair the (T14) Output Speed Sensor Signal circuit for a short to voltage.
- Perform AS68RC VERIFICATION TEST. AS68RC Transmission Verification Test

No

- Go To 8



8. CHECK THE (T72) SENSOR GROUND CIRCUIT FOR A SHORT TO VOLTAGE





Measure the voltage of the (T72) Sensor Ground circuit in the Output Speed Sensor harness connector.

Is there any voltage present?

Yes

- Repair the (T72) Sensor Ground circuit for a short to voltage.
- Perform AS68RC VERIFICATION TEST. AS68RC Transmission Verification Test

No

- Go To 9



9. REPLACE THE OUTPUT SPEED SENSOR

Replace the Output Speed Sensor.

Reconnect all connectors.

Clear DTCs and road test the vehicle under the conditions in which the original DTC set.

Did the loss of Output Speed Sensor/wheel speed DTC reset?

Yes

- Using the schematics as a guide, check the Transmission Control Module (TCM) pins, terminals, and connectors for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace and program the TCM.
- Perform AS68RC VERIFICATION TEST. AS68RC Transmission Verification Test

No

- Test complete.
- Perform AS68RC VERIFICATION TEST. AS68RC Transmission Verification Test



10. INTERMITTENT WIRING AND CONNECTORS

The conditions necessary to set this DTC are not present at this time.

Use the Freeze Frame Data to help duplicate the conditions in which the DTC originally set. Pay particular attention to the DTC set conditions, such as, VSS, MAP, ECT, and Load

Using the schematics as a guide, visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or partially broken wires.

Visually inspect the related wiring harness connectors. Look for broken, bent, pushed out, or corroded terminals.

Wiggle the wiring and connectors while checking for any possible open or shorted circuits.

Check for any Service Information Tune-ups or Technical Service Bulletins that may apply.

Were there any problems found?

Yes

- Repair as necessary.
- Perform AS68RC VERIFICATION TEST. AS68RC Transmission Verification Test

No

- Test Complete.
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