Multiplex Communication System - Diagnosis: Pre-Check

1. The BEAN communication line is used to control the following items:
   • Airbag sensor assy (Airbag ECU)
   • Combination meter assy (Meter ECU)
   • Power window regulator master switch assy A/C amplifier (A/C ECU)
   • Multiplex tilt & telescopic ECU
   • Transponder key ECU ECM
   • Center cluster integration switch assy
   • Network gateway ECU
   • Rain sensor
   • Sliding roof drive gear assy (Sliding roof ECU)
   • Headlamp swivel ECU (AFS ECU)
   • Multiplex network door ECU back (Power back door ECU)
   • Position control ECU & switch assy (Power seat ECU)
   • Telephone ECU (Mayday ECU)
   • Windshield wiper relay assy (Wiper ECU)
   • Driver side outer mirror control ECU
   • Passenger side outer mirror control ECU

   If there is a short-circuit (bus-down) in the line, communication to the system that has a short-circuit (bus-down) will be disabled and the DTC concerning the system will be output from the multiplex network body ECU.

   Fig 1: Identifying Multiplex Communication System (BEAN)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. If DTC indicating ECU communication stop is output, the connectors may be disconnected or the communication buses may be open at 2 points. Only 1 communication bus open will not set DTC.
   Fig 2: Identifying Disconnection (DTC Is Output)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
3. If 2 communication buses are open at the positions as shown in Fig 3 , DTC indicating ECU communication stop between those 2 buses is output.
   Fig 3: Identifying DTC Indicating Communication Stop Between 3 ECUs

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Inspect the DLC3.
   Fig 4: Inspecting DLC3

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   HINT:

   The vehicle's ECM uses ISO 9141-2 for communication.

   The terminal arrangement of the DLC3 complies with SAE J1962 and matches the ISO 9141-2 format.

   TERMINAL CONNECTION AND SPECIFIED CONDITION
   
   

   Terminal No.	Condition	Specified Condition
   7 (Bus + line) - 5 (Signal ground)	During communication	Pulse generation
   4 (Chassis ground) - Body ground	Constant	Below 1 Ω
   5 (Signal ground) - Body ground	Constant	Below 1 Ω
   16 (B+) - Body ground	Constant	9 to 14 V

   HINT:

   If the display shows UNABLE TO CONNECT TO VEHICLE when you have connected the cable of the hand-held tester to the DLC3, turned the ignition switch ON and operated the hand-held tester, there is a problem on the vehicle side or tester side.

   • If communication is normal when the tester is connected to another vehicle, inspect the DLC3 of the original vehicle.
   • If communication is still impossible when the tester is connected to another vehicle, the problem is probably in the tester itself, so consult the Service Department listed in the tester's instruction manual.
2. Check the battery voltage.

   Battery voltage: 11 to 14 V 

   If voltage is below 11V, recharge the battery before proceeding.

1. Connect the hand-held tester to the DLC3.
Fig 5: Connecting Hand-Held Tester To DLC3
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Turn the ignition switch ON.
3. Read DTCs by following the prompts on the tester screen.

HINT:

Refer to the hand-held tester operator's manual for further details.

1. Connect the hand-held tester to the DLC3.
2. Turn the ignition switch ON.
3. Erase the DTCs following the prompts on the tester screen.

HINT:

Refer to the hand-held tester operator's manual for further details.