Section 421 (Multiplex Communication System - Diagnostics): Pre-Check

1. As shown in Fig 1 , each ECU of this vehicle is connected by communication bus and it transmits each signal by communication. This communication bus is self-diagnosed by Body No. 1 ECU and it memorizes DTC when it detects communication stop to ECU or communication bus +B short or GND short. There is a possibility that Body No. 1 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 if Body No. 1 ECU and Open door indicator works normal by 2 "BASIC INSPECTION" described later.
   Fig 1: Multiplex Communication - Instrument Panel And Door System Communication Bus Diagram

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2. If DTC of ECU communication stop is output, 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: Communication Diagram - DTC Indicating ECU Communication Stop Is Output

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3. If 2 communication buses are open at the position as shown in Fig 3 , DTC of ECU communication stop between those 2 buses is output.
   Fig 3: Communication Diagram - Communication Buses Are Open At Positions

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Basic inspection is for checking Body No.1 ECU normal operation.

INSPECT BODY NO. 1 ECU 

1. Check Body No. 1 ECU operation. 

   HINT:

   With this inspection Body No. 1 ECU CPU can be diagnosed if it works normal or not.

   CHECK: 

   Check if the luggage compartment door opener works normal.

   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 luggage compartment door opener system (Except Body No. 1 ECU) (See  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. 

      HINT:

      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.

   HINT:

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

   Fig 4: Checking Open Door Indicator Light

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   1. OK: Go to step 4. 
   2. NG: Repair the open door indicator light (See  INSPECTION  ). 

      HINT:

      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

         Fig 5: Connecting Terminals TC And CG

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      2. Turn the ignition switch ON.
      3. Read the DTC from the open door indicator light.

      HINT:

      As an example, the blinking patterns for codes; normal, 12 and 11 and 12 are shown in Fig 6 .

      Fig 6: Example Blinking Indicator Patterns For Codes; Normal, 12 & 11 And 12

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   2. Check the problem using the DTC table shown in DIAGNOSTIC TROUBLE CODE CHART  .
   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 No.1 ECU is normal.

   1. OK: Go to Diagnosis trouble code chart (See  DIAGNOSTIC TROUBLE CODE CHART   ). 
   2. NG: Check the Body No.1 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.
      Fig 7: Connecting Hand-Held Tester To DLC3

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   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 book).

   CHECK: 

   Check the DTC.

   If no DTC is indicated, the Body No.1 ECU is normal.

   If Body No.1 ECU is abnormal, you can not select the "Body No.1 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 No.1 ECU power source (See  CIRCUIT 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.