How To Proceed With Troubleshooting
Carry out troubleshooting in accordance with the procedure below. Only a basic procedure is shown. Details in Diagnostics show the most effective methods for each circuit. Confirm troubleshooting procedures first for the relevant circuit before beginning troubleshooting of that circuit.
- CUSTOMER PROBLEM ANALYSIS
- The 5 items below are important points in the problem analysis:
- In troubleshooting, the problem symptoms must be confirmed accurately. Preconceptions should be discarded in order to give an accurate judgement. To ascertain what the problem symptoms are, it is extremely important to ask the customer about the problem and the conditions at the time it occurred.
Important Points in the Customer Problem Analysis
- What - Vehicle model, system name
- When - Date, time, occurrence frequency
- Where - Road conditions
- Under what conditions? - Running conditions, driving conditions, weather conditions
- How did it happen? - Problem symptoms
(Sample) Supplemental restraint system check sheet.
- SYMPTOM CONFIRMATION AND DIAGNOSTIC TROUBLE CODE CHECK
The diagnostic system in the RAV4 fulfills various functions.
- The first function is the Diagnostic Trouble Code (DTC) Check. In a DTC Check, a previous malfunction's DTC can be checked by a technician during troubleshooting. (A DTC is a code stored in the ECU memory whenever a malfunction in the signal circuits to the ECU occurs.)
- 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, the problem areas can be narrowed down and troubleshooting is more effective. Diagnostic functions are incorporated in the following systems in the RAV4.
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In the DTC Check, it is very important to determine whether the problem indicated by the DTC is: 1) still occurring, or 2) occurred in the past but has since returned to normal. In addition, the DTC should be compared to the problem symptom to see if they are related. For this reason, DTCs should be checked before and after confirmation of symptoms (i.e., whether or not problem symptoms exist) to determine current conditions, as shown in Fig 4.
Never skip the DTC Check. Failure to check DTCs may, depending on the case, result in unnecessary troubleshooting for systems operating normally or lead to repairs not pertinent to the problem. Follow the procedures listed above in the correct order.
DIAGNOSTIC TROUBLE CODE CHECK PROCEDURE
Taking into account the points in Fig 4, a flow chart showing how to proceed with troubleshooting using the diagnostic trouble code check is shown in Fig 5. Directions from the flow chart will indicate how to proceed to DTC troubleshooting or to the troubleshooting of problem symptoms table.
- SYMPTOM SIMULATION
The most difficult case in troubleshooting is when no problem symptoms occurring. In such cases, a thorough customer problem analysis must be carried out. Then simulate a simulation of the same or similar conditions and environment in which the problem occurred in the customer's vehicle should be carried out. No matter how much skill or experience a technician has, troubleshooting without confirming the problem symptoms will lead to something important in the repair operation being overlooked and lead to mistakes or delays in repairs.
For example:
With a problem that only occurs when the engine is cold, or occurs as result of vibration caused by road during driving, the problem can never be determined as long as the symptoms are being checked on stationary vehicle or a vehicle with a warmed-up engine.
Vibration, heat or water penetration (moisture) is difficult to reproduce. The symptom simulation tests below are effected substitutes for the conditions and can be applied on a stationary vehicle.
Important Points in the Symptom Simulation Test:
In the symptom simulation test, the problem symptoms as well as problem area or parts must be confirmed. First, narrow down the possible problem circuits according to the symptoms. Then, connect the tester and carry out the symptom simulation test, judging whether the circuit being tested is defective or normal, and also confirming the problem symptoms at the same time. Refer to the problem symptoms table for each system to narrow down the possible causes of the symptom.
- DIAGNOSTIC TROUBLE CODE CHART
Use Diagnostic Trouble Codes (DTCs) (from the DTC checks) in the tables to determine the trouble area and proper inspection procedure.
- PROBLEM SYMPTOMS TABLE
The suspected circuits or parts for each problem symptom are shown in the tables. Use this table to troubleshoot when, during a DTC check, a "Normal" code is displayed in the diagnostic trouble code check but the problem is still occurring. Numbers in the table show the inspection order in which the circuits or parts should be checked.
HINT:
In some cases, a problem is not detected by the diagnostic system even though a problem symptom is present. It is possible that the problem is occurring outside the detection range of the diagnostic system, or that the problem is occurring in a completely different system.
- CIRCUIT INSPECTION
Each Diagnostic Trouble Code (DTC) procedure, provides a circuit description, DTC detecting condition, trouble area and wiring diagram when applicable.
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002