AUTOMATIC TRANSMISSION (DIAGNOSTICS)(4AT) > Diagnostic Procedure without Diagnostic Trouble Code (DTC)

CHECK FWD SWITCH

DIAGNOSIS:

FWD signal circuit is open or shorted.

TROUBLE SYMPTOM:

The AWD warning light does not illuminate even with a fuse installed to the FWD switch.

WIRING DIAGRAM:

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1.CHECK SPARE FUSE.

Is the spare fuse OK?

Replace the fuse.

2.CHECK FWD SWITCH.

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

2) Install a fuse to the FWD switch.

3) Read the “FWD Switch” data using Subaru Select Monitor.

Is ON displayed?

3.CHECK COMBINATION METER.

Is the AWD warning light illuminated?

4.CHECK HARNESS CONNECTOR BETWEEN TCM AND FWD SWITCH.

1) Turn the ignition switch to OFF.

2) Disconnect the connector from TCM.

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

Connector & terminal

(B54) No. 10 — (B158) No. 7:

Is the resistance less than 1 Ω?

Repair the open circuit of harness between TCM and FWD switch connectors.

5.CHECK HARNESS CONNECTOR BETWEEN FWD SWITCH AND CHASSIS GROUND.

Measure the resistance of harness between FWD switch and chassis ground.

Connector & terminal

(i5) No. 13 — Chassis ground:

Is the resistance less than 1 Ω?

Repair the open circuit of harness between FWD switch connector and chassis ground.

6.CHECK HARNESS CONNECTOR BETWEEN TCM AND FWD SWITCH.

Measure the resistance of the harness connector between TCM and chassis ground to make sure that circuit is not shorted.

Connector & terminal

(B54) No. 10 — Chassis ground:

Is the resistance 1 MΩ or more?

Repair the short circuit of harness between TCM and FWD switch connectors.

7.CHECK INPUT SIGNAL FOR TCM.

1) Turn the ignition switch to OFF.

2) Connect the connector to TCM.

3) Turn the ignition switch to ON.

4) Measure the signal voltage for TCM while installing the fuse to FWD switch connector.

Connector & terminal

(B54) No. 10 (+) — Chassis ground (−):

Is the voltage less than 1 V?

8.CHECK INPUT SIGNAL FOR TCM.

Measure the signal voltage for TCM with the fuse removed from FWD switch connector.

Connector & terminal

(B54) No. 10 (+) — Chassis ground (−):

Is the voltage 9 V or more?

Replace the TCM.

9.CHECK BODY INTEGRATED UNIT.

Check DTC of body integrated unit.

Is DTC of CAN communication displayed?

Perform the diagnosis according to DTC.

10.CHECK COMBINATION METER.

Check the AWD warning light.

Is the AWD warning light OK?

Replace the combination meter assembly.

11.CHECK POOR CONTACT.

Is there poor contact in FWD switch circuit?

Repair the poor contact.

Replace the TCM.