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

DTC P0768 SHIFT SOLENOID “D” ELECTRICAL

DTC DETECTING CONDITION:

The output signal circuit of low & reverse duty solenoid is open or shorted.

TROUBLE SYMPTOM:

Gear is not changed.

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 harness between TCM connector and transmission connector.

Connector & terminal

(B54) No. 5 — (B11) No. 6:

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 CHASSIS GROUND.

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

Connector & terminal

(B54) No. 5 — Chassis ground:

Is the resistance 1 MΩ or more?

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

3.CHECK LOW & REVERSE DUTY SOLENOID.

Measure the resistance between transmission connector terminals.

Connector & terminal

(T4) No. 6 — No. 20:

Is the resistance 2.0 — 6.0 Ω?

4.CHECK OUTPUT SIGNAL OF TCM.

1) Connect all connectors.

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

3) Start the engine.

4) Run the Subaru Select Monitor.

5) Warm up the transmission until the ATF temperature exceeds approximately 80°C (176°F).

6) Stop the engine.

7) Turn the ignition switch to ON.

8) Set the select lever to “N” range.

9) Read the data of “L&R/B Duty” using Subaru Select Monitor.

Is the measured value 100%?

5.CHECK OUTPUT SIGNAL FROM TCM USING SUBARU SELECT MONITOR.

1) Lift up the vehicle.

2) Set the select lever to manual mode, and then hold it in 1st gear.

3) Slowly increase the vehicle speed up to 15 km/h (9 MPH), and then return the accelerator pedal.

4) Read the data of “L&R/B Duty” using Subaru Select Monitor.

NOTE:

The speed difference between front and rear wheels lights the ABS warning light or the VDC warning light, but this does not indicate a malfunction. If the warning light is illuminated, clear the memory of ABS or VDC after completing AT control diagnosis.

Is the measured value 55%?

Check the harnesses or connectors between TCM and transmission, and repair the defective part.

6.CHECK FOR POOR CONTACT.

Is there poor contact of the low & reverse duty solenoid circuit?

Repair the poor contact.

Replace the TCM.

7.CHECK LOW & REVERSE BRAKE DUTY SOLENOID (IN TRANSMISSION).

1) Remove the transmission connector from bracket.

2) Drain the automatic transmission fluid.

CAUTION:

Do not drain ATF until it cools down.

3) Remove the oil pan.

4) Disconnect the connector from the control valve body.

5) Measure the resistance between low & reverse duty solenoid connector and transmission ground.

Connector & terminal

(AT2) No. 1 — Transmission ground:

Is the resistance 2.0 — 6.0 Ω?

Replace the control valve body.

8.CHECK HARNESS CONNECTOR BETWEEN TRANSMISSION AND LOW & REVERSE DUTY SOLENOID.

Measure the resistance of harness between low & reverse duty solenoid and transmission connector.

Connector & terminal

(T4) No. 6 — (AT2) No. 1:

Is the resistance less than 1 Ω?

Repair open circuit of harness between low & reverse duty solenoid and transmission connector.

9.CHECK HARNESS CONNECTOR BETWEEN TRANSMISSION AND LOW & REVERSE DUTY SOLENOID.

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

Connector & terminal

(T4) No. 6 — Transmission ground:

Is the resistance 1 MΩ or more?

Check the harnesses or connectors between low & reverse duty solenoid and transmission, and repair the defective part.

Repair the short circuit of the harness between the low & reverse duty solenoid and the transmission connector.