Diagnostic Test

WARNING: This page is about a different car, the 2005 Jeep Grand Cherokee. However, it is still accessible from the selected car via links, so may be relevant.

1) CHECK TO SEE IF DTC P0720 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 ROTATING WHEELS.

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

Is the Output Speed Sensor RPM below 100 RPM?

Yes
1. Go To step 2).
No
1. Go To step 9).
2) OUTPUT SPEED SENSOR
Turn the ignition off to the lock position.

Remove the Starter Relay.

NOTE: Removal of the Starter Relay is to prevent a Transmission, NO RESPONSE, condition and disable the starter.

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 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
1. Replace the Output Speed Sensor per the Service Information.
2. Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .
No
1. Go To step 3).
3) OUTPUT SPEED SENSOR SIGNAL CIRCUIT OPEN

Fig 1: Checking Output Speed Sensor Signal Circuit for Open
Courtesy of DAIMLERCHRYSLER CORP.

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 Output Speed Sensor Signal circuit from the Output Speed Sensor harness connector to the appropriate terminal of special tool #8815.

Is the resistance above 5.0 ohms?

Yes
1. Repair the Output Speed Sensor Signal circuit for an open.
2. Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .
No
1. Go To step 4).
4) SPEED SENSOR GROUND CIRCUIT OPEN

Fig 2: Checking Speed Sensor Ground Circuit for Open
Courtesy of DAIMLERCHRYSLER CORP.

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

Is the resistance above 5.0 ohms?

Yes
1. Repair the Speed Sensor Ground circuit for an open.
2. Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .
No
1. Go To step 5).
5) OUTPUT SPEED SENSOR SIGNAL CIRCUIT SHORT TO GROUND

Fig 3: Checking Output Speed Sensor Signal Circuit for Short to Ground
Courtesy of DAIMLERCHRYSLER CORP.

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

Is the resistance below 5.0 ohms?

Yes
1. Repair the Output Speed Sensor Signal circuit for a short to ground.
2. Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .
No
1. Go To step 6).
6) SPEED SENSOR GROUND CIRCUIT SHORT TO GROUND

Fig 4: Checking Speed Sensor Ground Circuit for Short to Ground
Courtesy of DAIMLERCHRYSLER CORP.

Measure the resistance between ground and the Speed Sensor Ground circuit.

Is the resistance below 5.0 ohms?

Yes
1. Repair the Speed Sensor Ground circuit for a short to ground.
2. Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .
No
1. Go To step 7).
7) OUTPUT SPEED SENSOR SIGNAL CIRCUIT SHORT TO VOLTAGE

Fig 5: Checking Output Speed Sensor Signal Circuit for Short
Courtesy of DAIMLERCHRYSLER CORP.

Remove the Transmission Control Relay.

Place a jumper wire between the Fused B+ circuit and the Transmission 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
1. Repair the Output Speed Sensor Signal circuit for a short to voltage.
2. Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .
No
1. Go To step 8).
8) SPEED SENSOR GROUND CIRCUIT SHORT TO VOLTAGE

Fig 6: Checking Speed Sensor Ground Circuit for Short to Voltage
Courtesy of DAIMLERCHRYSLER CORP.

Measure the voltage of the Speed Sensor Ground circuit.

Is the voltage above 0.5 volts?

Yes
1. Repair the Speed Sensor Ground circuit for a short to voltage.
2. Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .
No
1. 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 per the Service Information. With the scan tool, perform QUICK LEARN.
2. Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .
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 EATX DTC EVENT DATA to help identify the conditions in which the DTC was set.

Were there any problems found?

Yes
1. Repair as necessary.
2. Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .
No
1. Test Complete.