Section 922 (Multiplex Communication System - Diagnostics): Pre-Check

1. The BEAN communication line consists of 2 systems:

   One is a system with a loop-shaped line that the back door ECU is united with the body ECU present in the center of the line. Another is a system that the body ECU and the theft deterrent ECU are connected alone.

   Since the line for the back door ECU is loop-shaped, the communication can be maintained by the line that is not open even if part of the line become open for some reason. In the case that there is a short-circuit (bus-down) in the line, however, all the BEAN communication becomes impossible in the system and some DTCs are output.

   HINT:

   • When bus-down occurs, communication from the related ECU stops. Therefore, DTC cannot be output, so perform a DTC (SAE code) inspection using the hand-held tester.
   • The theft deterrent ECU and the back door ECU have a single communication line. Therefore, if the line has a short-circuit (bus-down), the BEAN communication will be impossible and DTCs will not be output, either.

1. Inspect the battery voltage.

   Standard: 10-14 V 

2. Inspect the diagnosis monitor code output.
   1. Check a diagnosis code for the body ECU by connecting the hand-held tester to the DLC3 and turning the ignition switch ON.
   2. When the display shows diagnostic codes of the ECU unconnected and the communication bus defective, perform the inspection depending on the troubleshooting.

HINT:

When other diagnostic code is output, refer to the diagnostic code table and check the applicable section.