Diagnostic Procedures

The diagnostic procedures used in this article are designed to find and repair engine performance related problems. The general approach to solving a problem is to follow four basic steps. The detailed procedure is contained within the "PFI SYSTEM CHECK  ". The four basic steps are:

1. Are The On Car Diagnostics Working Properly
   
   Use the "PFI SYSTEM CHECK  " . This is the starting point for the diagnostic procedure, always begin here. If the Diagnostics are not working properly, the "PFI System Check" will lead you to a chart to correct this condition. If the engine will not start or stalls, see PFI CHART A-3: NO START OR STALL AFTER START  . If the Diagnostics are working, the next step is:
2. Is There A Trouble Code Displayed
   
   If a trouble code is identified by diagnostics, the "PFI SYSTEM CHECK  " will direct you to the appropriate PFI chart . Refer to "TROUBLE CODE DISPLAY  " later in this article for the correct procedure to display trouble codes. If no trouble codes are stored, the next step is:
3. Do All Switch Tests Pass
   
   If a switched input to the ECM is not indicating the proper status and change-of-state, Input Displays  should be referenced for diagnosis. If all switched inputs are operating correctly, the next step is:
4. Is The Fuel System Controlling Correctly
   
   The "PFI SYSTEM CHECK  " will be used to correct the problem. If the "PFI System Check" shows that the system is in closed loop and operating normally, go to TROUBLE SHOOTING - NO CODES article.