Diagnostic Strategies

EXPLANATION OF TROUBLESHOOTING PROCEDURES
Effective troubleshooting procedures related to problems of the MFI system are described below.

1. Confirmation of the malfunction.
- Cause the malfunction to reoccur and check the details of the malfunction and the conditions (engine condition, driving conditions, etc.) when the malfunction reoccurs.
2. Read-out of the diagnostic trouble code.
- When the diagnostic trouble code is read out and the diagnostic trouble code is output, refer to the diagnostic chart and repair the indicated location of the malfunction.
3. Assumption to the probable cause of the malfunction, and determination of the appropriate check points.
- Refer to the "CHECK CHART CLASSIFIED BY PROBLEM SYMPTOMS" and confirm the sequence of checking for the indicated malfunction.
4. Checking of the engine control module's input and output signals.
- Using the scan tool or an oscilloscope, check the input and output signals of the engine control module.
- If the input and output signals are normal, sensor input/ actuator control can be judged to be normal, so check the input and output signals of the subsequent check point.
5. Checking of the MFI component's harness.
- If an abnormal condition of the input and output signals of the engine control module is discovered, check, and repair if necessary, the body harness of the MFI component.
- After making this repair, again check the input and output signals of the engine control module; if they are normal, proceed to the checking of the input and output signals of the subsequent check point.
6. Checking of the MFI component itself.
- If the input and output signals of the engine control module are abnormal even though the body harness is normal, check the MFI component itself, and repair or replace as necessary.
- After making this repair or replacement, again check the input and output signals of the engine control module; if they are normal, proceed to the checking of the input and output signals of the subsequent check point.
7. Rechecking of the cause of the malfunction, and repair.
- If the input and output signals of the engine control module are abnormal even though the harness checking and the checking of the unit itself indicate that the condition is normal, refer to the troubleshooting hints to recheck the probable cause, and then check other groups and repair as necessary.
8. Confirmation that repair procedures have been completed and that reoccurrence has been prevented.
- Perform a test to try to get the malfunction to reoccur, and confirm that it does not.
- Eliminate the true cause of the malfunction so as to prevent its reoccurrence.