DTC B1278: Combination Switch ECU Communication Stop: Procedure

1. Disconnect the J26 connector.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

2. Measure the voltage and resistance according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   J26-1 (B) - Body ground	Always	11 to 14 V
   J26-2 (IG) - Body ground	Engine switch on (IG)	11 to 14 V

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   J26-5 (E) - Body ground	Always	Below 1 Ω

   TEXT IN ILLUSTRATION
   
   

   *1	Front view of wire harness connector (to Windshield Wiper Switch Assembly)

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Disconnect the J76 and J55 connectors.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

2. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   J26-6 (MPX1) - J76-12 (MPD2)	Always	Below 1 Ω
   J26-7 (MPX2) - J55-7 (MPX1)	Always	Below 1 Ω

   TEXT IN ILLUSTRATION
   
   

   *1	Front view of wire harness connector (to Windshield Wiper Switch Assembly)
   *2	Front view of wire harness connector (to Gateway ECU)
   *3	Front view of wire harness connector (to Power Source Control ECU)

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Replace the windshield wiper switch assembly. Refer to REMOVAL [08/2012 - ] .

NEXT: Go to next step 

1. Clear the DTC. Refer to DTC CHECK / CLEAR [08/2012 - ] .
2. Recheck for DTCs.

   OK

   DTC B1278 is not output.

NG → See step   5 

OK → END (WINDSHIELD WIPER SWITCH ASSEMBLY WAS DEFECTIVE)