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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 448 (Engine Controls Self-Diagnostics - 6.0L Bi-Fuel & CNG) >> Diagnostic Tests >> DTC P0148: Fuel Delivery Error >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2003 GMC Savana and 2003 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
    2. NOTE: Verify that there is adequate fuel in the CNG fuel tank before proceeding.
  2. Turn ignition on, with engine off. Observe the FUEL MODE COMMAND parameter using a scan tool. If the scan tool displays ALT FUEL, go to next step. If the scan tool does not display ALT FUEL, go to step  4.
  3. Observe the Freeze Frame and/or the Failure records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and/or the Failure records data. If the DTC failed this ignition cycle, go to next step. If the DTC does not fail this ignition cycle, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
  4. Turn ignition off. Disconnect the Fuel Injection Control Module (FICM). Probe the AF enable circuit with a test light connected to battery positive. If the test light illuminates, go to step  7. If test light does not illuminate, go to next step.
  5. Turn ignition on. Command the AF enable circuit ON and OFF using a scan tool. Observe the test light. If the test light responds to the scan tool commands, go to step  9. If the test light does not respond to the scan tool commands, go to next step.
  6. Test the AF enable circuit for an open. Did you find and correct an open? If yes, go to step  12. If no, go to step  8.
  7. Test the AF enable circuit for a short to ground. Did you find and correct a short to ground? If yes, go to step  12. If no, go to step  10.
  8. Test for an intermittent and/or a poor connection at the PCM. Did you find and correct an intermittent condition? If yes, go to step  12. If no, go to step  10.
  9. Test for an intermittent and/or a poor connection at the FICM. Did you find and correct an intermittent condition? If yes, go to step  12. If no, go to step  11.
  10. Replace the PCM. After replacement is complete, go to step  12.
  11. Replace the FICM. After replacement is complete, go to step  12.
  12. Observe the Freeze Frame/Failure Records for this DTC. Turn the ignition off for 30 seconds. Turn ignition on, with engine off. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. If the DTC failed this ignition cycle, go to step  2. If the DTC did not fail this ignition cycle, go to next step.
  13. Observe the Capture Info using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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