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.
   Fig 4: Identifying Open Door Indicator Light

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   1. OK : Go to step 4. 
   2. NG : Repair the open door indicator light (See step 27  CIRCUIT  ). 
   NOTE: If repairing or replacing malfunction part, please repeat step 3.
4. DTC Check (Using diagnosis check wire) 

   CHECK:

   1. Using diagnosis check wire.
      1. Using SST, connect terminals Tc and CG of DLC3.

         SST 09843-18040

      2. Turn the ignition switch ON.
      3. Read the DTC from the open door indicator light.
      Fig 5: Identifying Terminals Tc And CG Of DLC3

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      NOTE: As an example, the blinking patterns for codes; normal, 12, and 11 and 12 are shown in the illustration.
      Fig 6: Identifying Blinking Patterns For Codes: Normal, 12, 11 And 12

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   2. Check the problem using the DTC table on the next section.
   3. After completing the check, turn the ignition switch off, and disconnect terminals Tc and CG.

   CHECK:

   Check the indicator blinking patterns.

   If normal code is indicated, the Body ECU is normal.

   1. OK : Go to Diagnosis trouble code chart (See  DIAGNOSTIC TROUBLE CODE CHART  ). 
   2. NG : Check the Body ECU power source (See  CIRCUIT INSPECTION  ). 

5. DTC Check (Using hand-held tester) 
   1. Prepare the hand-held tester.
   2. Connect the hand-held tester to DLC3.
   3. Turn the ignition switch ON and the hand-held tester main switch ON.
   4. Check the DTCs and note them down (When using hand held tester, see the hand-held tester's instruction manual).
   Fig 7: Connecting Hand-Held Tester To DLC3

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   CHECK:

   Check the DTC.

   If no DTC is indicated, the Body ECU is normal.

   If Body ECU is abnormal, you can not select the "Body ECU" in the hand-held tester screen.

   1. OK : Go to Diagnosis trouble code chart (See  DIAGNOSTIC TROUBLE CODE CHART  ). 
   2. NG : Check the Body ECU power source (See  INSPECTION  ). 

A Multiplex DTC indicates that a problem has been detected in the Multiplex System. Once the problem is corrected and the system begins to operate as designed, the DTC will be cleared automatically. There is no need to manually clear a multiplex DTC using the hand-held tester.