AUTOMATIC TRANSMISSION (DIAGNOSTICS)(4AT) > Diagnostic Procedure with Diagnostic Trouble Code (DTC)

DTC P0720 OUTPUT SPEED SENSOR CIRCUIT

DTC DETECTING CONDITION:

• The vehicle speed signal is abnormal.

• The harness connector between TCM and vehicle speed sensor is shorted or open.

TROUBLE SYMPTOM:

• Neutral control does not operate.

• Slip lock up control does not operate.

• Driving performance is poor.

WIRING DIAGRAM:

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1.CHECK HARNESS CONNECTOR BETWEEN TCM AND TRANSMISSION.

1) Turn the ignition switch to OFF.

2) Disconnect the connectors from TCM and transmission.

3) Measure the resistance of the harness between TCM connector and transmission connector.

Connector & terminal

(B55) No. 27 — (B11) No. 14:

Is the resistance less than 1 Ω?

Repair the open circuit of harness between TCM and transmission connector.

2.CHECK HARNESS CONNECTOR BETWEEN TCM AND TRANSMISSION.

Measure the resistance of the harness between TCM connector and transmission connector.

Connector & terminal

(B55) No. 16 — (B11) No. 18:

Is the resistance less than 1 Ω?

Repair the open circuit of harness between TCM and transmission connector, and poor contact of the connector.

3.CHECK HARNESS CONNECTOR BETWEEN TCM AND TRANSMISSION.

Measure the resistance of the harness between TCM connector and chassis ground.

Connector & terminal

(B55) No. 27 — Chassis ground:

Is the resistance 1 MΩ or more?

Repair the short circuit in the harness between the TCM and chassis ground.

4.CHECK HARNESS CONNECTOR BETWEEN TCM AND TRANSMISSION.

Measure the resistance of the harness between TCM connector and chassis ground.

Connector & terminal

(B55) No. 16 — Chassis ground:

Is the resistance 1 MΩ or more?

Repair the short circuit of the harness and poor contact of connectors between the TCM and chassis ground.

5.CHECK FRONT VEHICLE SPEED SENSOR.

Measure the resistance between transmission connector receptacle’s terminals.

Connector & terminal

(T4) No. 14 — No. 18:

Is the resistance 450 — 650 Ω?

Replace the front vehicle speed sensor.

6.CHECK INPUT SIGNAL FOR TCM USING SUBARU SELECT MONITOR.

1) Connect all connectors.

2) Connect the Subaru Select Monitor to the data link connector.

3) Lift up the vehicle.

4) Turn the ignition switch to ON.

5) Run the Subaru Select Monitor.

6) Start the engine.

7) Read the data of “Front Wheel Speed” using Subaru Select Monitor.

8) Compare the speedometer with Subaru Select Monitor indications.

9) Slowly increase the vehicle speed to 60 km/h (37 MPH).

NOTE:

The speed difference between the front and rear wheels will illuminate the ABS warning light or VDC warning light, but this does not indicate a malfunction. If the warning light illuminates, delete the ABS or VDC memory after completing the AT control diagnosis.

Does the speedometer indication increase as the Subaru Select Monitor front wheel speed data increases?

Check for poor contact in the front vehicle speed sensor circuit harness and repair the fault location.

7.CHECK FOR POOR CONTACT.

Is there poor contact in front vehicle speed sensor circuit?

Repair the poor contact.

Replace the TCM.