SystemDiagnostic TroubleCode CheckInput Signal Check(Sensor Check)Other DiagnosisFunctionEngineAutomatic TransmissionAnti–Lock Brake System (& Traction Control)Supplemental Restraint SystemCruise Controlf(with Test Mode)f(with Test Mode)fffffffDiagnostic TestModeDiagnostic TestModeIn diagnostic trouble code check, it is very important to determine whether the problem indicated by the diag-nostic trouble code is still occurring or 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 diagnostictrouble code is directly related to the problem symptom or not. For this reason, the diagnostic trouble codesshould be checked before and after the symptom confirmation to determine the current conditions, as shownin the table below. If this is not done, it may, depending on the case, result in unnecessary troubleshootingfor normally operating systems, thus making it more difficult to locate the problem, or in repairs not pertinentto the problem. Therefore, always follow the procedure in correct order and perform the diagnostic troublecode check.
Diagnostic trouble code checkMaking a note of and clearing of the diagnostic trouble codes displayedSymptom confirmationNo problem symptomsexistProblem symptoms existSimulation test using the symptom simulation methodsDNormal code displayedDProblem symptoms existDNormal code displayedDNo problem symptoms existDiagnostic trouble code checkTroubleshooting of problem indicatedby diagnostic trouble codeDDiagnostic trouble code displayedDProblem symptoms existSystem NormalTroubleshooting of each problem symptomIf a diagnostic trouble code was displayed in the initial diagnostictrouble code check, it indicatesthat the trouble may have occurredin a wire harness or connector inthat circuit in the past. Therefore,check the wire harness and con-nectors (See page IN–27).IN–20–INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS20AuthorĂ:DateĂ:1997 LEXUS ES300 (RM511U)Taking into account the above points, a flow chart showing how to proceed with troubleshooting using thediagnostic trouble code check is shown below. This flow chart shows how to utilize the diagnostic troublecode check effectively, then by carefully checking the results, indicates how to proceed either to diagnostictrouble code troubleshooting or to troubleshooting of problem symptoms.
V07268VIBRATION METHOD: When vibration seems to be the major cause.CONNECTORSWIRE HARNESSPARTS AND SENSOR1Slightly shake the connector vertically and horizontally.Slightly shake the wire harness vertically and horizontally.The connector joint, fulcrum of the vibration, and bodythrough portion are the major areas to be checked thorough-ly.
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Lexus, Engine control unit, LEXUS ES300, diagnostic trouble