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Diagnostic Procedure

WARNING: This page is about a different car, the 2005 Jeep Liberty. However, it is still accessible from the selected car via links, so may be relevant.
DIAGNOSTIC TEST REFERENCE - P0720-OUTPUT SPEED SENSOR ERROR

TEST ACTION APPLICABILITY
1
NOTE: Low fluid level can be the cause of many transmission problems. If the fluid level is low locate and repair the leak then check and adjust the fluid level per the Service Information.
NOTE: Always perform diagnostics with a fully charged battery to avoid false symptoms.
With the DRBIII®, read the engine DTC's. Check and repair all engine DTC's prior to performing transmission symptom diagnostics.With the DRBIII®, read Transmission DTC's. Record all DTC's and 1 Trip Failures.
NOTE: Diagnose 1 Trip Failures as a fully matured DTC.
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors. Repair as necessary.Perform the Shift Lever Position Test. If the test does not pass, refer to Symptom test for P0706 CHECK SHIFTER SIGNAL .For Gear Ratio DTC's, check and record all CVI's.Most DTC's set on start up but some must be set by driving the vehicle such that all diagnostic monitors have run.
NOTE: Verify the flash level of the transmission controller. Some problems are corrected by software upgrades to the transmission controller.
NOTE: Check for applicable TSB's related to the problem.
Perform this procedure prior to Symptom diagnosis.ContinueGo To 2		 All
2 Turn the ignition off to the lock position.
CAUTION: Properly support the vehicle and raise all drive wheels off the ground.

Start the engine in park.
Place the transmission gear selector in drive, release foot from brake.
CAUTION: BE SURE TO KEEP HANDS AND FEET CLEAR OF ROTATING WHEELS.

With the DRBIII®, monitor the Output Speed Sensor RPM.
Is the Output Speed Sensor RPM below 100 RPM?
Yes --> Go To 3
No --> Go To 12		 All
3 Turn the ignition off to the lock position.
Remove the Starter Relay.
NOTE: Failure to remove the Starter Relay can cause a Transmission - No Response condition.

Install the Transmission Simulator, Miller tool #8333.
NOTE: Check connectors - Clean/repair as necessary.

Ignition on, engine not running.
With the Transmission Simulator, set the "Input/Output Speed" switch to "ON" and the rotary switch to the "3000/1000" position.
With the DRBIII®, read the Input and Output Speed Sensor readings.
Does the Input Speed read 3000 RPM and the Output Speed read 1000 RPM, +/- 50 RPM?
Yes --> Go To 4
No --> Go To 5		 All
4 If there are no possible causes remaining, view repair.
Repair
Replace the Output Speed Sensor per the Service Information.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .		 All
5 Turn the ignition off to the lock position.
Disconnect the TCM harness connector.
Disconnect the Output Speed Sensor harness connector.
NOTE: Check connectors - Clean/repair as necessary.

Measure the resistance of the Output Speed Sensor Signal circuit from the TCM harness connector to the Output Speed Sensor harness connector.
Is the resistance above 5.0 ohms?
Yes --> Repair the Output Speed Sensor Signal circuit for an open.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .
No --> Go To 6		 All
6 Turn the ignition off to the lock position.
Disconnect the TCM harness connector.
Disconnect the Output Speed Sensor harness connector.
NOTE: Check connectors - Clean/repair as necessary.

Measure the resistance between ground and the Output Speed Sensor Signal circuit.
Is the resistance Below 5.0 ohms?
Yes --> Repair the Output Speed Sensor Signal circuit for a short to ground.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .
No --> Go To 7		 All
7 Turn the ignition off to the lock position.
Disconnect the TCM harness connector.
Remove the Transmission Control Relay.
NOTE: Check connectors - Clean/repair as necessary.

Place a jumper wire between the Fused B+ circuit and the Transmission Control Relay Output circuit in the Transmission Control Relay connector.
Ignition on, engine not running.
Measure the voltage of the Output Speed Sensor Signal circuit.
Is the voltage above 0.5 volts?
Yes --> Repair the Output Speed Sensor Signal circuit for a short to voltage.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .
No --> Go To 8		 All
8 Turn the ignition off to the lock position.
Disconnect the TCM harness connector.
Disconnect the Output Speed Sensor harness connector.
NOTE: Check connectors - Clean/repair as necessary.

Measure the resistance of the Speed Sensor Ground circuit from the TCM harness connector to the Output Speed Sensor harness connector.
Is the resistance above 5.0 ohms?
Yes --> Repair the Speed Sensor Ground circuit for an open.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .
No --> Go To 9		 All
9 Turn the ignition off to the lock position.
Disconnect the TCM harness connector.
Disconnect the Output Speed Sensor harness connector.
NOTE: Check connectors - Clean/repair as necessary.

Measure the resistance between ground and the Speed Sensor Ground circuit.
Is the resistance below 5.0 ohms?
Yes --> Repair the Speed Sensor Ground circuit for a short to ground.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .
No --> Go To 10		 All
10 Turn the ignition off to the lock position.
Disconnect the TCM harness connector.
Remove the Transmission Control Relay.
NOTE: Check connectors - Clean/repair as necessary.

Place a jumper wire between the Fused B+ circuit and Transmission Control Relay Output circuit in the Transmission Control Relay connector.
Ignition on, engine not running.
Measure the voltage of the Speed Sensor Ground circuit.
Is the voltage above 0.5 volts?
Yes --> Repair the Speed Sensor Ground circuit for a short to voltage.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .
No --> Go To 11		 All
11 Using the schematics as a guide, inspect the wiring and connectors. Repair as necessary. Pay particular attention to all power and ground circuits.
If there are no possible causes remaining, view repair.
Repair
Replace the Transmission Control Module per the Service Information. WITH THE DRBIII® PERFORM QUICK LEARN .
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .		 All
12 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 shorts and open circuits.
With the DRBIII®, check the EATX 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 - VER 1 .
No --> Test Complete.		 All
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