Diagnostic Procedures

The diagnostic procedures used in this section 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
   
   We determine this by using the "PFI SYSTEM CHECK  ". Since this is the starting point for the diagnostic procedure, always begin here. If the On Car 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 after start, see PFI CHART A-3: NO START OR STALL AFTER START  . If the On Car Diagnostics are OK, continue to the next step.
2. Is There A Trouble Code Displayed
   
   If a trouble code is identified using the self diagnostics, a problem has been detected by the system which can be corrected by following the "PFI SYSTEM CHECK  " which will direct you to the appropriate chart. If no trouble codes are stored, continue to the next step.
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, continue to the next step.
4. Is The Fuel System Controlling Correctly
   
   We find this out by using the "PFI Fuel System Control Check" contained within the "PFI SYSTEM CHECK  ". If the "PFI Fuel System Control Check" shows that the system is in closed loop and operating normally, refer to 1989 TROUBLE SHOOTING - NO CODES -- ALLANTE article.

This quick test, which takes only a couple of minutes, can save a lot of time, and lead you to the correct procedure to repair the problem.