Toyota Highlander Service Manual: Symptom confirmation and diagnostic trouble code
HINT: The diagnostic system in the HIGHLANDER has various functions.
- The first function is the Diagnostic Trouble Code (DTC) check. A DTC is a code stored in the ECU memory whenever a malfunction in the signal circuits to the ECU occurs. In a DTC check, a previous malfunction's DTC can be checked by a technician during troubleshooting.
- Another function is the Input Signal Check, which checks if the
signals from various switches are sent
to the ECU correctly.
By using these functions, the problem areas can be narrowed down and troubleshooting is more effective.
Diagnostic functions are incorporated in the following systems in the HIGHLANDER:
- 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 the table below.
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.
- A flow chart showing how to proceed with troubleshooting using the DTC check is shown below. Directions from the flow chart will indicate should be performed DTC troubleshooting or to the troubleshooting of each problem symptom.
1 DTC CHECK
2 MAKE A NOTE OF DTCS DISPLAYED AND THEN CLEAR THE MEMORY
3 SYMPTOM CONFIRMATION
| a | Symptoms exist |
| b | No symptoms exist |
4 SIMULATION TEST USING THE SYMPTOM SIMULATION METHODS
5 DTC CHECK
| a | DTC displayed |
| b | No DTC displayed |
6 SYMPTOM CONFIRMATION
| a | No symptoms exist |
| b | Symptoms exist |
If a DTC was displayed in the initial DTC check, it indicates that the trouble may have occurred in a wire harness or connector in that circuit in the past. Check the wire harness and connectors (see page 01-36 ).
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 a secondary problem).
Customer problem analysis
HINT:
In troubleshooting, the problem symptoms must be confirmed
accurately. Preconceptions should be
discarded in order to give an accurate judgement. To clearly understand what
the probl ...
Symptom simulation
HINT:
The most difficult case in troubleshooting is when no problem symptoms occur. In
such cases, a thorough
customer problem analysis must be carried out. A simulation of the same or
similar c ...
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