System Diagnosis - With Port Fuel Injection (PFI)

Diagnostic Circuit Check:

DIAGNOSTIC CIRCUIT CHECK

The Diagnostic Circuit Check must be the starting point for any driveability complaint diagnosis.


The diagnostic circuit check is an organized approach to identifying a problem created by an electronic engine control system malfunction because it directs the service technician to the next logical step in diagnosing the complaint.

If after completing the diagnostic circuit check and finding the on-board diagnostics functioning properly and no trouble codes displayed, a comparison of "Typical Scan Values", for the appropriate engine, may be used for comparison. The "Typical Values" are an average of display values recorded from normally operating vehicles and are intended to represent what a normally functioning system would display.

A "SCAN" TOOL THAT DISPLAYS FAULTY DATA SHOULD NOT BE USED, AND THE PROBLEM SHOULD BE REPORTED TO THE MANUFACTURER. THE USE OF A FAULTY "SCAN" CAN RESULT IN MISDIAGNOSIS AND UNNECESSARY PARTS REPLACEMENT.

Only the parameters listed are used for diagnosis. If a "Scan" reads other parameters, the values are not recommended for use in diagnosis. For more description on the values and use of the "Scan" to diagnose Electronic Control Module (ECM) inputs, refer to the Scan Tester Diagnosis. If all values are within the range illustrated, refer to Diagnosis By Symptoms - No Trouble Codes Stored.