Subaru Legacy BN/BS (2015-2019) Service Manual: Dtc p0720 output shaft speed sensor circuit

Subaru Legacy BN/BS (2015-2019) Service Manual / Continuously variable transmission (diagnostics) / Diagnostic procedure with diagnostic trouble code (dtc) / Dtc p0720 output shaft speed sensor circuit

DTC DETECTING CONDITION:

Immediately at fault recognition

TROUBLE SYMPTOM:

• Shock occurs when selecting shift position.

• Shift control malfunction

WIRING DIAGRAM:

CVT control system CVT Control System > WIRING DIAGRAM

STEP	CHECK	YES	NO
1.CHECK FUSE. 1) Turn the ignition switch to OFF. 2) Check the M/B fuse No. 26.	Is the fuse OK-	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0720 OUTPUT SHAFT SPEED SENSOR CIRCUIT	Replace the fuse. If the fuse blows out easily, repair the short circuit of harness.
2.CHECK ECM CONNECTOR. Check the connecting condition of ECM connector.	Is the ECM connector correctly connected-	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0720 OUTPUT SHAFT SPEED SENSOR CIRCUIT	Connect the ECM connector correctly.
3.CHECK HARNESS BETWEEN TRANSMISSION CONNECTOR AND MAIN RELAY CONNECTOR. 1) Turn the ignition switch to OFF. 2) Measure the voltage between transmission connector and engine ground. Connector & terminal (B22) No. 7 (+) — Engine ground (−):	Is the voltage 10 V or more-	Repair the harness and connector. NOTE: In this case, repair the following item: • Short circuit to power supply of harness between transmission connector and main relay connector • Defective main relay	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0720 OUTPUT SHAFT SPEED SENSOR CIRCUIT
4.CHECK HARNESS BETWEEN ECM AND MAIN RELAY CONNECTOR. 1) Turn the ignition switch to OFF. 2) Remove the main relay. 3) Disconnect the connector from ECM. 4) Measure the resistance between the ECM connector and engine ground. Connector & terminal (B134) No. 60 — Engine ground:	Is the resistance 1 M- or more-	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0720 OUTPUT SHAFT SPEED SENSOR CIRCUIT	Repair the short circuit to ground in harness between ECM connector and main relay connector.
5.CHECK HARNESS. 1) Turn the ignition switch to OFF. 2) Disconnect the TCM and transmission connectors. 3) Measure the resistance between TCM connector and transmission connectors. Connector & terminal (B54) No. 12 — (B22) No. 12: (B54) No. 26 — (B22) No. 20: (B54) No. 42 — (B22) No. 13:	Is the resistance less than 1 --	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0720 OUTPUT SHAFT SPEED SENSOR CIRCUIT	Repair the open circuit of harness.
6.CHECK HARNESS. Measure the resistance between TCM connector and chassis ground. Connector & terminal (B54) No. 12 — Chassis ground:	Is the resistance 1 M- or more-	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0720 OUTPUT SHAFT SPEED SENSOR CIRCUIT	Repair the short circuit of harness.
7.CHECK TRANSMISSION HARNESS. 1) Install the fuse. 2) Connect the TCM connector. 3) Turn the ignition switch to ON. 4) Measure the voltage between transmission connector terminals. Connector & terminal (B22) No. 7 (+) — Chassis ground (−):	Is the voltage approx. 10 — 13 V-	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0720 OUTPUT SHAFT SPEED SENSOR CIRCUIT	Repair the poor contact of harness or connector.
8.CHECK INPUT SIGNAL FOR TCM. 1) Turn the ignition switch to OFF. 2) Connect the transmission connector. 3) Lift up the vehicle. 4) Start the engine. 5) Slowly increase the speed to 30 km/h (19 MPH). 6) Read the data of «Front Wheel Speed» using Subaru Select Monitor.	Does the value of «Front Wheel Speed» change according to the engine speed-	Current condition is normal. Repair the poor contacts of harnesses of front wheel speed sensor and transmission connector.	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0720 OUTPUT SHAFT SPEED SENSOR CIRCUIT
9.CHECK TRANSMISSION HARNESS. 1) Turn the ignition switch to OFF. 2) Disconnect the transmission connector. 3) Disconnect the front wheel speed sensor connector. 4) Measure the resistance between transmission connector and front wheel speed sensor connector. Connector & terminal (T4) No. 7 — (AT5) No. 1: (T4) No. 12 — (AT5) No. 2: (T4) No. 13 — (AT5) No. 3: (T4) No. 20 — (AT5) No. 3:	Is the resistance less than 1 --	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0720 OUTPUT SHAFT SPEED SENSOR CIRCUIT	Replace the transmission harness.
10.CHECK FRONT WHEEL SPEED SENSOR. 1) Turn the ignition switch to OFF. 2) Replace the front wheel speed sensor. Front Wheel Speed Sensor 3) Perform the Clear Memory Mode. Clear Memory Mode 4) Read the DTC.	Is DTC P0720 displayed-	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0720 OUTPUT SHAFT SPEED SENSOR CIRCUIT	The original front wheel speed sensor is defective.
11.CHECK MAIN RELAY. 1) Turn the ignition switch to OFF. 2) Replace the main relay. 3) Perform the Clear Memory Mode. Clear Memory Mode 4) Read the DTC.	Is DTC P0720 displayed-	Replace the TCM. Transmission Control Module (TCM)	The original main relay is defective.

1. OUTLINE OF DIAGNOSIS

• Detect no input signal from the front wheel speed sensor.

• Judge as NG if there is no output from the front wheel speed sensor while the forward/reverse clutch is engaged and the wheel speed from VDC is equal to or higher than the predetermined value.

2. EXECUTION CONDITION

Secondary Parameters	Execution condition
12 V battery system voltage	≥ 10 V
Vehicle speed (from vehicle dynamics control module)	≥ 3 MPH
Transmission range	Drive or Reverse

3. DIAGNOSTIC METHOD

If the duration of time while the following conditions are met is longer than the time indicated, judge as NG.

Judgment Value

Malfunction Criteria	Threshold Value
Measured front output shaft speed	0 rpm

Time Needed for Diagnosis: 0.5 seconds

Malfunction Indicator Light Illumination: Illuminates as soon as a malfunction occurs.

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