DTC U1822: Lost Communication With Master Main Switch

WARNING: This page is about a different car, the 2022 Subaru WRX. However, it is still accessible from the selected car via links, so may be relevant.

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>POWER WINDOW SYSTEM>WIRING DIAGRAM

Courtesy of SUBARU OF AMERICA, INC.

CAUTION:

Before performing diagnosis, refer to "CAUTION" in "General Description". Ref. to BODY CONTROL (DIAGNOSTICS)>GENERAL DESCRIPTION>CAUTION

CHECK DTC .
1. Turn the ignition switch to OFF.
2. Turn the ignition switch to ON.
3. Wait for 10 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 code)

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 BODY INTEGRATED UNIT CUSTOMIZATION .
Using Subaru Select Monitor, make sure the [Customize] setting values of [Body Control] correspond to the vehicle.

Does the set value of [P/W ECU Setting] correspond to the vehicle?

Yes : Go to 3.

No : Change the set value according to the vehicle.
CHECK HARNESS (OPEN CIRCUIT) .
1. Turn the ignition switch to OFF.
2. Disconnect the connector from body integrated unit.
3. Disconnect the connector from the power window main switch.
4. Using a tester, measure the resistance between the body integrated unit connector and power window main switch connector.
  Connector & terminal
  
  (i83) No. 2 - (Df34) No. 13:
Is the resistance less than 10 Ω?

Yes : Go to 4.

No : Repair the open circuit of harness.
CHECK HARNESS (SHORT CIRCUIT TO POWER SUPPLY) .
1. Turn the ignition switch to ON.
2. Measure the voltage between power window main switch connector and body integrated unit connector and chassis ground.
  Connector & terminal
  
  (i83) No. 2 (+) - Chassis ground (-):
  
  (Df34) No. 13 (+) - Chassis ground (-):
Is the voltage less than 1 V?

Yes : Go to 5.

No : Repair the short circuit to power supply in harness.
CHECK HARNESS (GROUND SHORT CIRCUIT) .
1. Turn the ignition switch to OFF.
2. Measure the resistance between power window main switch connector and body integrated unit connector and chassis ground.
  Connector & terminal
  
  (i83) No. 2 - Chassis ground:
  
  (Df34) No. 13 - Chassis ground:
Is the resistance 1 MΩ or more?

Yes : Replace the body integrated unit. Ref. to BODY CONTROL/COMMUNICATION SYSTEM>BODY INTEGRATED UNIT

No : Repair the ground short circuit of harness.