DTC U1670: Lin Communication Bus 2 Error Keyless Access With Push Button Start

DTC detecting condition: 

When LIN communication error is detected 3 times in a row.

(Communication cannot be received because a problem occurs such as a series of noise continuously generated in LIN communication bus during power supply or ground short circuit in LIN communication bus)

Trouble symptom: 

Hands-free function may not be operable.

Wiring diagram: 

Power rear gate system Refer to WIRING SYSTEM>Power Rear Gate System>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK DTC  .
   1. Using the Subaru Select Monitor, perform the clear memory of [Keyless Access with Push Button Start(Collation)]. Refer to COMMON (DIAG)>CLEAR MEMORY .
   2. Read the DTC of [Keyless Access with Push Button Start(Collation)] using the Subaru Select Monitor. Refer to KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC 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.
2. CHECK HARNESS (BETWEEN KEYLESS ACCESS Control Module AND HANDSFREE SENSOR)  .
   1. Disconnect the ground terminal from battery sensor. Refer to REPAIR CONTENTS>NOTE>BATTERY .
   2. Disconnect the keyless access Control Module connector.
   3. Disconnect the handsfree sensor connector.
   4. Using the tester, measure the resistance between terminals.

   Connector & terminal 

   (i92) No. 23 - (Db38) No. 2:

   Is the resistance less than 1 Ω?

   Yes:  Go to  3.

   No  : Repair or replace the open circuit of harness.

3. CHECK HARNESS (GROUND SHORT CIRCUIT)  .

   Using a tester, measure the resistance between keyless access Control Module connector or handsfree sensor connector and chassis ground.

   Connector & terminal 

   (i92) No. 23 - Chassis ground:

   (Db38) No. 2 - Chassis ground:

   Is the resistance 10 kΩ or more?

   Yes:  Go to  4.

   No  : Repair or replace the short circuit of the harness.

4. CHECK HARNESS (SHORT CIRCUIT TO POWER SUPPLY)  .

   Using a tester, measure the voltage between keyless access Control Module connector or handsfree sensor connector and chassis ground.

   Connector & terminal 

   (i92) No. 23 (+) - Chassis ground (-):

   (Db38) No. 2 (+) - Chassis ground (-):

   Is the voltage 1 V or less?

   Yes:  Go to  5.

   No  : Repair or replace the short circuit of the harness.

5. CHECK KEYLESS ACCESS Control Module  .
   1. Connect the keyless access Control Module connector.
   2. Using the Subaru Select Monitor, perform the clear memory of [Keyless Access with Push Button Start(Collation)]. Refer to COMMON (DIAG)>CLEAR MEMORY .
   3. Read the DTC of [Keyless Access with Push Button Start(Collation)] using the Subaru Select Monitor. Refer to KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC U1670 displayed? (Current malfunction)

   Yes:  Replace the keyless access Control Module. Refer to SECURITY AND LOCKS>KEYLESS ACCESS Control Module .

   No  : Go to  6.

6. CHECK HANDSFREE SENSOR  .
   1. Connect the handsfree sensor connector.
   2. Using the Subaru Select Monitor, perform the clear memory of [Keyless Access with Push Button Start(Collation)]. Refer to COMMON (DIAG)>CLEAR MEMORY .
   3. Read the DTC of [Keyless Access with Push Button Start(Collation)] using the Subaru Select Monitor. Refer to KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC U1670 displayed? (Current malfunction)

   Yes:  Replace the handsfree sensor. Refer to SECURITY AND LOCKS>HANDSFREE POWER REAR GATE>REMOVAL>HANDSFREE SENSOR .

   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.