Diagnostic Procedure

The Cadillac DFI engine control system is equipped with a self-diagnostic capability. This capability makes engine/engine system diagnosis much faster than in past systems. When a failure occurs, a "trouble code" is stored in the ECM. These codes indicate the general area of engine malfunction, NOT the specific component at fault. By following specific testing procedures, diagnosis of the system should determine the faulty component in the shortest period of time. Diagnosis of the system is carried out in 3 basic steps:

1. Begin with the "DFI SYSTEM CHECK" chart. This chart confirms operation of the self-diagnostic system. If the diagnostic system is not operating properly, this chart will direct you to another chart to correct the malfunction. If ECM self-diagnostic system is operating properly, go to next step.
   NOTE: If vehicle will not start, or stalls after starting, go to CHART A3, "NO START OR STALL AFTER START".
2. Withdraw any stored trouble codes from the ECM memory and determine which codes are "hard" codes and which ones are "intermit- tent". Diagnose any stored hard codes (and certain specific intermit- tent codes) with the trouble code flow charts. If no trouble codes are stored, go to next step.
3. Use "Field Service Mode Check" contained within the DFI SYSTEM CHECK chart to determine if fuel system is operating properly. If fuel system is not operating properly, another chart will be called out for correcting problem. If fuel system is not operating properly, symptom diagnosis will be referred to for possible correction.