DTC U1602: Lost Communication With Hands Free Sensor

DTC detecting condition:

No data is received from handsfree sensor.

Trouble symptom:

Handsfree function may not operate normally.

Wiring diagram:

Power rear gate system Ref. to WIRING SYSTEM>POWER REAR GATE SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

CAUTION:

For replacement procedure of keyless access control module, refer to the "REGISTRATION MANUAL FOR IMMOBILIZER" provided as a separate volume.
Before performing diagnosis, refer to "CAUTION" in "General Description". Ref. to KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM (DIAGNOSTICS)>General Description>CAUTION .

CHECK DTC .
1. Turn the ignition switch to ON.
2. Read the DTC of [Keyless Access with Push Button Start(Collation)] using the Subaru Select Monitor. Ref. to Keyless Access with Push Button Start System (Diagnostics)>Diagnostic Trouble Code (DTC) .
Is DTC U1602 or U1670 displayed? (Current malfunction)

Yes : Go to 2 .

No : Even if DTC is displayed, the circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis again.

NOTE: In this case, temporary poor contact of connector, temporary open or short circuit of harness may be the cause.
CHECK HARNESS (OPEN CIRCUIT) .
1. Turn the ignition switch to OFF.
2. Disconnect the handsfree sensor connector and the keyless access control module connector.
3. Using the tester, measure the resistance between terminals.
  Connector and terminal
  
  (Db38) No. 2 - (i92) No. 23:
Is the resistance less than 10 Ω?

Yes : Go to 3 .

No : Repair the open circuit of harness.
CHECK HARNESS (GROUND SHORT CIRCUIT) .
Using a tester, measure the resistance between handsfree sensor connector terminal and chassis ground.

Connector and terminal

(Db38) No. 2 - Chassis ground:

Is the resistance 10 kΩ or more?

Yes : Go to 4 .

No : Repair the shorted portion of harness.
CHECK HARNESS (SHORT CIRCUIT TO POWER SUPPLY) .
1. Turn the ignition switch to ON.
2. Using a tester, measure the voltage between handsfree sensor connector terminal and chassis ground.
  Connector and terminal
  
  (Db38) No. 2 (+) - Chassis ground (-):
Is the voltage less than 1 V?

Yes : Go to 5 .

No : Repair the shorted portion of harness.
CHECK KEYLESS ACCESS CONTROL MODULE .
1. Turn the ignition switch to OFF.
2. Replace the handsfree sensor with a properly functioning part.
3. Turn the ignition switch to ON.
4. Read the DTC of [Keyless Access with Push Button Start(Collation)] using the Subaru Select Monitor. Ref. to Keyless Access with Push Button Start System (Diagnostics)>Diagnostic Trouble Code (DTC) .
Is DTC U1602 or U1670 displayed? (Current malfunction)

Yes : Replace the keyless access control module. Ref. to SECURITY AND LOCKS>KEYLESS ACCESS CONTROL MODULE .

No : Malfunction occurred in the handsfree sensor.