Symptom Confirmation And Diagnostic Trouble Code

HINT:

• The diagnostic system in LEXUS ES300 has various functions. The first function is the Diagnostic Trouble Code (DTC) Check in which a malfunction in the signal circuits to the ECU is stored in code form in the ECU memory. Another function is the Input Signal Check which checks if the signals from various switches are sent to the ECU correctly. By using these check functions, possible areas of the problem can be narrowed down quickly and troubleshooting can be performed effectively. Diagnostic functions are incorporated in the following systems in LEXUS ES300.
  SYMPTOM CONFIRMATION AND DIAGNOSTIC TROUBLE CODE
  
  

  System	Diagnostic Trouble Code Check	Input Signal Check (Sensor Check)	Diagnostic Test Mode (Active Test)
  SFI System	X (with Check Mode)	X	X
  Electronic Modulated Suspension System	X		X
  ABS with EBD System	X	X	X
  ABS with EBD & BA & TRAC & VSC System	X	X	X
  Electronic Controlled Automatic Transmission [ECT]	X (with Check Mode)	X
  Air Conditioning System	X	X
  Supplement Restraint System	X
  Power Window Control System			X
  Power Door Lock Control System	X
  Wireless Door Lock Control System	X
  Engine Immobiliser System	X
  Multiplex Communication System	X
  Cruise Control System	X	X

• In the DTC check, it is very important to determine whether the problem indicated by the DTC is still occurring or has occurred in the past but returned to normal at present. In addition, it must be checked in the problem symptom check whether the malfunction indicated by the DTC is directly related to the problem symptom or not. For this reason, the DTC should be checked before and after the symptom confirmation to determine the current conditions. If this is not done, it may, depending on the case, result in an unnecessary troubleshooting for normally operating systems, making it more difficult to detect the problem area, or trying to repair irrelevant areas. Therefore always follow the procedure in the correct order and perform the DTC check.
• A flow chart showing how to proceed with the troubleshooting using the diagnostic trouble code (DTC) check is shown below. This flow chart shows how to utilize the DTC check effectively. Then, by carefully checking the results, indicates how to proceed either to the DTC troubleshooting or to the troubleshooting of problem symptoms table.

1. DTC check 
2. Making a note and clearing of the DTCs displayed 
3. Symptom confirmation 
   SYMPTOM CONFIRMATION
   
   

   a	Problem symptoms exist
   b	No problem symptoms exist

   1. a : Go to step   5 . 
   2. b : Go to next step. 
4. Simulation test using the symptom simulation methods 
5. DTC check 
   DTC CHECK
   
   

   a	DTC displayed
   b	Normal code displayed

   1. a : Troubleshooting of problem indicated by DTC 
   2. b : Go to next step. 
6. Symptom confirmation 
   SYMPTOM CONFIRMATION
   
   

   a	No problem symptoms exist
   b	Problem symptoms exist

   If a DTC is displayed in the initial DTC check, it indicates that a trouble may have occurred in a wire harness or connector in that circuit in the past, therefore check the wire harness and connectors (See ELECTRONIC CIRCUIT INSPECTION PROCEDURE  ).

   1. a : System normal 
   2. b : Troubleshooting of each problem symptom 

   The problem is still occurring in a place other than the diagnostic circuit (The DTC displayed first is either for a past problem or it is a secondary problem).