Section 553 (Multiplex Communication System - Diagnostics): Pre-Check

1. As shown in the following illustration, each ECU of vehicle is connected by communication bus and transmit each signal by communication. This communication bus is self-diagnosed by Body ECU and memorizes DTC when it detects communication stop to ECU or communication bus +B short or GND short. There is a possibility that Body ECU cannot self-diagnose accurately unless it doesn't work normal. So, please note that the troubleshooting of Body Electrical System should be done after confirming Body ECU and Open door indicator to work normally by 2 "BASIC INSPECTION", which is described later.
   Fig 1: Multiplex Communication System Signal Transmission Diagram

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2. If DTC of ECU communication stop is indicated, there is a possibility of connector disconnection or 2 communication buses open. It will not become abnormal with only 1 communication bus open.
   Fig 2: Identifying DTC Of ECU Communication Indications

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3. If 2 communication buses are open at the position as shown in the illustration, DTC of ECU communication stop between those 2 buses is indicated.
   Fig 3: Example - DTC Of ECU Communication

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Basic inspection is for checking Body ECU normal operation.

INSPECT BODY ECU 

1. Check Body ECU operation. 
   NOTE: With this inspection, Body ECU CPU can be diagnosed if it works normal or not.

   CHECK:

   Check if the rear washer motor works normally.

   1. OK : Go to step   3  (Using diagnosis check wire) Go to step   5  (Using hand-held tester) 
   2. NG : Go to Next Step 
2. Check rear wiper system (Except Body ECU), (See step 4 and 8  INSPECTION  ). 
   1. OK : Go to step 3 (Using diagnosis check wire) Go to step   5  (Using hand-held tester) 
   2. NG : Repair or replace malfunction part. 
   NOTE: If repairing or replacing malfunction part, please repeat step 1.
3. Check open door indicator light. 

   CHECK:

   Check if open door Indicator light comes on when either door is open.

   NOTE: If open door Indicator light is not turned on, DTC will not be output.