DTC U1822: Lost Communication With Master Main Switch

DTC detecting condition: 

Data does not arrive from power window main switch.

Trouble symptom: 

LIN communication is not normal.

Wiring diagram: 

Power window system Ref. to WIRING SYSTEM (IMPREZA MODEL)>POWER WINDOW SYSTEM>WIRING DIAGRAM . Ref. to WIRING SYSTEM (CROSSTREK MODEL (EXCEPT FOR HEV))>POWER WINDOW SYSTEM>WIRING DIAGRAM . Ref. to WIRING SYSTEM (CROSSTREK MODEL (HEV))>POWER WINDOW SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK DTC  .
   1. Turn the ignition switch to OFF.
   2. Turn the ignition switch to ON.
   3. Wait for 5 seconds.
   4. Read the DTC of [Body Control] using the Subaru Select Monitor. Ref. to BODY CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

      Is DTC U1822 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 (OPEN CIRCUIT)  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the body integrated unit connector.
   3. Disconnect the power window main switch connector.
   4. Measure the resistance between body integrated unit connector and power window main switch connector.

      Connector & terminal 

      (i81) No. 2 - (D7) No. 13:

      Is the resistance less than 10 Ω?

      Yes  : Go to  3.

      No  : Repair the open circuit of harness.

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

   Measure the voltage between power window main switch connector and body integrated unit connector and chassis ground.

   Connector & terminal 

   (i81) No. 2 (+) - Chassis ground (-):

   (D7) No. 13 (+) - Chassis ground (-):

   Is the voltage less than 1 V?

   Yes  : Go to  4.

   No  : Repair the short circuit to power supply in harness.

4. CHECK HARNESS (GROUND SHORT CIRCUIT)  .

   Measure the resistance between power window main switch connector and body integrated unit connector and chassis ground.

   Connector & terminal 

   (i81) No. 2 (+) - Chassis ground (-):

   (D7) No. 13 (+) - Chassis ground (-):

   Is the resistance 1 MΩ or more?

   Yes  : Replace the body integrated unit. Ref. to SECURITY AND LOCKS>BODY INTEGRATED UNIT .

   No  : Repair the ground short circuit of harness.