Multiplex Communication System - Diagnostics: Pre-Check

1. The BEAN communication line is used for the body, meters and air conditioning controls. Since the line is loop-shaped, the communication can be kept by the line that is not open even if a part of the line becomes open for some reasons. In case that the line becomes short (bus-down) for some reasons, however, all the BEAN communication will be impossible and some DTC will be output.

HINT:

When a bus-down occurs, the communication from the related ECU will stop. Therefore, an outputs of a DTC will be impossible. So, perform a DTC (SAE code) inspection with the hand-held tester.

1. Inspect the battery positive voltage.

   Standard:10 - 14 V 

2. Perform a DTC check of the body ECU by connecting the hand-held tester to the DLC3 and turning the ignition switch ON.
   1. Check that the DTCs of the ECU unconnected and also a short-circuit in the communication bus are not output.

1. Inspect the battery positive voltage.

   Standard: 10 - 14 V (when engine stopped) 

2. Check the DTC output.

1. Check that the door open indicator will be on when any of the doors is opened.

   HINT:

   In case that the indicator will not be on, the following problems are possible reasons; door open indicator LED defective, wire harness short, courtesy light switch's contact condition defective, multiplex network body ECU defective, etc.

   Fig 1: Identifying DLC3 Connector Terminals

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Using SST (diagnosis check wire), make a short circuit between terminals TC (13) and CG (4) of the DLC3 connector.

   SST 09843-18040

   NOTE: Do not make a short-circuit in any other positions.
3. Turn the ignition (starter) switch ON and read the number of blinks of the door open indicator.

   HINT:

   When 2 or more codes are output simultaneously, the display will be started from the smallest numbered code.

   Fig 2: Identifying Door Open Indicator Blinking Pattern

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
4. When the DTC of the ECU unconnected is displayed, perform an inspection depending on the troubleshooting.

HINT:

• When the communication bus is defective, the door open indicator in the meter will not be on. Therefore no DTC will be output.
• When other DTCs are output, refer to the DTC chart and applicable section.
• When no normal output is output even in the normal condition, problems, such as a short-circuit between terminals TC and CG, meter fuses defective, etc., may exist.
• When the door open indicator is always on, the wire harness might be short-circuited.

1. Inspect the battery positive voltage.

   Standard: 10 -14 V 

2. Inspect the DTC monitor code output.
   1. Connect the hand-held tester to the DLC3 and turn the ignition (starter) switch ON, then check the DTC.

      HINT:

      When the DTC check is impossible, check the following items.

      • ECU data monitor is possible (multiplex network body ECU is defective).
      • The display shows a communication error (refer to the new diagnostic system and operations when an error occurred). (See HOW TO PROCEED WITH TROUBLESHOOTING )
   2. When the display shows DTCs that the ECU is unconnected and the communication bus is defective, perform an inspection depending on the troubleshooting.

   HINT:

   When other DTCs are output, refer to the DTC chart and applicable section.