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 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 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 ECU and Open door indicator works normal by 2 "BASIC INSPECTION" described later.
   Fig 1: ECU Communication 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 Busses Are Open At Positions

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Basic inspection is for checking Body ECU normal operation.

INSPECT BODY ECU 

1. Check Body ECU operation. 

   HINT:

   With this inspection, Body ECU CPU can be diagnosed if it works normal or not.

   CHECK: 

   Check if the luggage compartment door opener works normally.

   OK: Go to step   3  (using diagnosis check wire) Go to step   5  (using hand-held tester) 

   NG: Go to next step. 

2. Check luggage compartment door opener system (Except Body ECU) (See  INSPECTION  ). 

   OK: Go to step 3 (using diagnosis check wire) Go to step   5  (using hand-held tester) 

   NG: Repair of 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 come 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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   OK: Go to step 4. 

   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.
         1. SST 09843-18040
         Fig 5: Connecting Terminals TC & CG

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

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

   2. Check for the problem using the DTC table on the next page.
   3. After completing the check, turn the ignition switch off, and disconnect terminals TC and CG.
   Fig 6: Example Of Normal 12 And 11 & 12 Codes Blinking Pattern

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5. DTC Check (Using LEXUS hand-held tester) 
   1. Prepare the LEXUS hand-held tester.
   2. Connect the LEXUS hand-held tester to DLC3.
      Fig 7: Connecting Lexus Hand-Held Tester To DLC3

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   3. Turn the ignition switch ON and the LEXUS hand-held tester main switch ON.
   4. Check the DTCs, note them down (When using LEXUS hand-held tester, see the hand-held tester's instruction book).
   5. See DIAGNOSTIC TROUBLE CODE CHART  to confirm the details of the DTCs.

   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 LEXUS hand-held tester screen.

   OK: Go to Diagnosis trouble code chart (See  DIAGNOSTIC TROUBLE CODE CHART  ). 

   NG: Check the Body 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 LEXUS hand-held tester.