545RFE Automatic Transmission

P0721-OUTPUT SPEED SENSOR CIRCUIT PERFORMANCE





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


Theory of Operation


The transmission system uses two speed sensors, one to measure input rpm and one to measure output rpm. These inputs are essential for proper transmission operation. Therefore, the integrity of this data is verified through the following checks:


1) When in gear, if the gear ratio does not compare to a known gear ratio, the corresponding in-gear trouble code is set (DTCs P0731-36, P1736 and P1776).


2) An excessive change in input or output speeds indicating signal intermittent will result in codes P0716 and/or P0721 being set.


3) If the common speed sensor ground circuit is lost, both sensor inputs will read the signal from the input speed sensor at idle in neutral. Since the input speed sensor has 60 teeth and the output speed sensor has 30 teeth, this results in a an apparent speed ratio of 1:2 and may cause the DTC P1794 to set.


- When Monitored:

The transmission gear ratio is monitored continuously while the transmission is in gear.

- Set Condition:

If there is an excessive change in output rpm in any gear. This DTC can take up to five minutes of problem identification before illuminating the MIL.







Always perform the 45RFE/545RFE Pre-Diagnostic Troubleshooting Procedure before proceeding. 45RFE/545RFE Pre-Diagnostic Troubleshooting Procedure



Diagnostic Test


1. CHECK TO SEE IF DTC P0721 IS CURRENT

Turn the ignition off to the lock position.


CAUTION: Properly support the vehicle and raise all drive wheels off the ground.

Release the parking brake.

Start the engine in park.

Place the transmission gear selector in drive, release foot from brake.


WARNING: Be sure to keep hands and feet clear of rotation wheels.

With the scan tool, monitor the Output Speed Sensor rpm.

Is the Output Speed Sensor rpm below 100 rpm?

Yes

- Go To 2

No

- Go To 9



2. OUTPUT SPEED SENSOR

Turn the ignition off to the lock position.

Remove the Ignition Switch Feed fuse from the TIPM.


CAUTION: Removal of the Ignition Switch Feed fuse from the TIPM will prevent the vehicle from being started in gear.


WARNING: The Ignition Switch Feed fuse must be removed from the TIPM. Failure to do so can result in personal injury or death.

Install the Transmission Simulator, Miller tool #8333.

Ignition on, engine not running.

With the Transmission Simulator, set the selector switch to 3000/1000 and the Input/Output switch to ON.

With the scan tool, monitor the Input and Output Speed Sensor rpm

Does the Input Speed read 3000 rpm and the Output Speed read 1000 rpm, ± 50 rpm?

Yes

- Replace the Output Speed Sensor.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. 45RFE/545RFE Transmission Verification Test

No

- Go To 3



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





Turn the ignition off to the lock position.

Disconnect the Transmission Simulator, Miller tool #8333.

Disconnect the PCM harness connectors and connect Miller special tool #8815.


CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller special tool #8815 to perform diagnosis.

Measure the resistance of the (T14) Output Speed Sensor Signal circuit from the Output Speed Sensor harness connector to the appropriate terminal of Miller tool #8815.

Is the resistance above 5.0 ohms?

Yes

- Repair the (T14) Output Speed Sensor Signal circuit for an open.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. 45RFE/545RFE Transmission Verification Test

No

- Go To 4



4. CHECK THE (T13) SPEED SENSOR GROUND CIRCUIT FOR AN OPEN





Measure the resistance of the (T13) Speed Sensor Ground circuit from the Output Speed Sensor harness connector to the appropriate terminal in the Miller tool #8815.

Is the resistance above 5.0 ohms?

Yes

- Repair the (T13) Speed Sensor Ground circuit for an open.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. 45RFE/545RFE Transmission Verification Test

No

- Go To 5



5. 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 5.0 ohms?

Yes

- Repair the (T14) Output Speed Sensor Signal circuit for a short to ground.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. 45RFE/545RFE Transmission Verification Test

No

- Go To 6



6. CHECK THE (T13) SPEED SENSOR GROUND CIRCUIT FOR A SHORT TO GROUND





Measure the resistance between ground and the (T13) Speed Sensor Ground circuit.

Is the resistance below 5.0 ohms?

Yes

- Repair the (T13) Speed Sensor Ground circuit for a short to ground.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. 45RFE/545RFE Transmission Verification Test

No

- Go To 7



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





Ignition on, engine not running.

With the scan tool in TIPM, actuate the TCM output.

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

Is the voltage above 0.5 volts?

Yes

- Repair the (T14) Output Speed Sensor Signal circuit for a short to voltage.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. 45RFE/545RFE Transmission Verification Test

No

- Go To 8



8. CHECK THE (T13) SPEED SENSOR GROUND CIRCUIT FOR A SHORT TO VOLTAGE





With the scan tool in TIPM, actuate the TCM output.

Measure the voltage of the (T13) Speed Sensor Ground circuit.

Is the voltage above 0.5 volts?

Yes

- Repair the (T13) Speed Sensor Ground circuit for a short to voltage.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. 45RFE/545RFE Transmission Verification Test

No

- Using the schematics as a guide, check the Powertrain Control Module (PCM) terminals for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace the PCM. With the scan tool, perform QUICK LEARN.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. 45RFE/545RFE Transmission Verification Test



9. INTERMITTENT WIRING AND CONNECTORS

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

Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.

Wiggle the wires while checking for shorted and open circuits.

With the scan tool, check the DTC EVENT DATA to help identify the conditions in which the DTC was set.

Were there any problems found?

Yes

- Repair as necessary.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. 45RFE/545RFE Transmission Verification Test

No

- Test Complete.