Malfunction Symptoms And DTC Check

NOTE: The diagnostic system has various functions. When a malfunction occurs in the signal circuit to the ECM, the corresponding code is stored in the ECM memory, and this is output as a diagnostic code during troubleshooting. This diagnostic function has been included so that you can freely use it to rapidly narrow down the scope of the malfunction and perform effective troubleshooting. It is extremely important to check diagnostic codes in order to determine if the malfunction indicated by the diagnostic code is still occurring, or if the malfunction occurred in the past but now operation has returned to normal. Additionally, it is necessary to check using malfunction phenomenon inspection to determine if the malfunction indicated by the diagnostic code is directly related to the malfunction phenomenon.
For this reason, it is necessary to check the diagnostic code before and after checking the malfunction phenomenon in order to determine the current conditions. Failure to do this results in, depending on the conditions, having to perform unnecessary troubleshooting of systems that might be operating normally, making it difficult to locate the malfunction location and the performance of repairs unrelated to the malfunction. For this reason, it is necessary to always check diagnostic codes in the correct order of the procedure.

NOTE:

The following is a flowchart that shows how to perform troubleshooting using diagnostic code checking.
This flowchart indicates how to effectively use diagnostic code checking, and procedures for performing diagnostic code and malfunction phenomenon troubleshooting by carefully checking the results of the diagnostic code check.

Malfunction identification (Interview)
Next

DTC check

Read out all DTCs.

Result

Result	Go to
Diagnostic code is present.	A
Cannot read out from all connected ECMs.	B
No diagnostic code	C

B: Bus (communication lines) failure (Refer to HOW TO TROUBLESHOOT for CAN bus failure and to HOW TO TROUBLESHOOT LIN failure.)

C: Go to Step 7.

A: Go to next step

Save diagnostic codes and freeze frame data

Save output diagnostic codes and freeze frame data.

CAUTION:

Do not delete before saving. Deleting these will result in the deletion of all diagnostic codes, freeze frame data and history data.
Write down the panel diagnosis information as it cannot be saved.

NOTE:

When multiple codes are output, identify the main cause by all diagnostic codes.
For systems in which ECM data can be checked, use input-period estimation data (data monitor).
There are output diagnostic codes even if there is no malfunction. (Such as air conditioning sunload sensor and learning not performed after battery disconnection.)

Result

Result	Go to
Communication diagnostics and other diagnostics are present	A
Other than communication diagnostics	B
Communication diagnostics only	C

B: Go to Step 5.

C: Bus (communication lines) failure (Refer to HOW TO TROUBLESHOOT for CAN bus failure and to HOW TO TROUBLESHOOT LIN failure.)

A: Go to next step

Isolate malfunction cause

From all the diagnostic codes, determine whether main cause is in parts or bus (communication line).

NOTE: It is possible to be tailgating output of communication diagnostics due to a parts malfunction.

Result

Result	Go to
Part failure	A
Bus (communication line) failure	B

B: Bus (communication lines) failure troubleshooting (Refer to HOW TO TROUBLESHOOT for CAN communication system and to HOW TO TROUBLESHOOT for the large-scale multiplex communication system for vehicle body [LIN].)

A: Go to next step

Clear diagnostic codes and freeze frame data.
Next

Driving test, DTC check

Result

Result	Go to
No diagnostic code	A
Diagnostic code is present.	B

B: Perform troubleshooting according to the flowchart by diagnostic code.

A: Perform simulation test using the simulation procedures of the malfunction phenomenon.

Check malfunction phenomenon
1. Use the interview results and data monitor to determine whether the customer's indications are malfunction.
  NG: Perform troubleshooting according to the flowchart by symptom.
  
  OK: System normal