Symptom Confirmation And Diagnostic Trouble Code Check

The diagnostic system in the TERCEL fulfills various functions. The first function is the Diagnostic Trouble Code Check in which a malfunction in the signal circuits to the ECU is stored in code in the ECU memory at the time of occurrence, to be output by the 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 check functions, the problem areas can be narrowed down quickly and troubleshooting can be performed effectively. Diagnostic functions are incorporated in the following systems in the TERCEL.

System

Diagnostic Trouble Code Check

Input Signal Check (Sensor Check)

Diagnostic Test Mode (Active Test)

1. Engine

(with Check Mode)

o

O

2. Anti-Lock Brake System

O

o

3. Supplemental Restraint System

O

4. Power Door Lock Control System

5. Theft Deterrent System

In diagnostic trouble code check, it is very important to determine whether the problem indicated by the diagnostic 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 diagnostic trouble code is directly related to the problem symptom or not. For this reason, the diagnostic trouble codes should be checked before and after the symptom confirmation to determine the current conditions, as shown in the table below. If this is not done, it may, depending on the case, result in unnecessary troubleshooting for normally operating systems, thus making it more difficult to locate the problem, or in repairs not pertinent to the problem. Therefore, always follow the procedure in correct order and perform the diagnostic trouble code check.

DIAGNOSTIC TROUBLE CODE CHECK PROCEDURE

Diagnostic Trouble Code Check (Make a note of and then clear)

Confirmation of Symptoms

Diagnostic Trouble Code Check

Problem Condition

Diagnostic Trouble Code Display

Problem symptoms exist >

Same diagnostic trouble code is displayed

Problem is still occurring in the diagnostic circuit

Normal code is displayed

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

No problem symptoms exist

The problem occurred in the diagnostic circuit in the past

Normal Code Display^

Problem symptoms exist

Normal code is displayed

The problem is still occurring in a place other than in the diagnostic circuit

No problem symptoms exist

Normal code is displayed

The problem occurred in a place other than in the diagnostic circuit in the past

Taking into account the points on the previous page, a flow chart showing how to proceed with troubleshooting using the diagnostic trouble code check is shown below. This flow chart shows how to utilize the diagnostic trouble code check effectively, then by carefully checking the results, indicates how to proceed either to diagnostic trouble code troubleshooting or to troubleshooting of problem symptoms table.

Diagnostic trouble code check

Making a note of and clearing of the diagnostic trouble codes displayed

Symptom confirmation

Problem symptoms exist

No problem symptoms exist

Simulation test using the symptom simulation methods

Diagnostic trouble code check

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