Horn Circuit [12/2019 - 11/2023]: Procedure

1. Press the horn switch and check if the horn sounds.

   Result

   Result	Proceed to
   Horn sounds	A
   Horn does not sound	B

Result: 

B 

GO TO HORN SYSTEM. Refer to  PROBLEM SYMPTOMS TABLE [12/2019 - 11/2023] 

Result: 

A 

See step  2

1. Remove the main body ECU (multiplex network body ECU).

   Refer to REMOVAL [12/2019 - 10/2022] , or refer to REMOVAL [10/2022 - 11/2023]

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a

   Component without harness connected (Instrument Panel Junction Block Assembly)

   -

   -

2. Disconnect the 4C instrument panel junction block assembly connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   4C-27 - MB-28 (HORN)	Always	Below 1 Ω

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU). Refer to  REMOVAL [12/2019 - 10/2022]  , or refer to  REMOVAL [10/2022 - 11/2023] 

Result: 

NG 

REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY. Refer to  REMOVAL [12/2019 - 10/2022]  , or refer to  REMOVAL [10/2022 - 11/2023]