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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 452 (Engine Controls - Self-Diagnostics - 6.0L Bi-Fuel & CNG) >> Self-Diagnostic System >> Diagnostic System Check - Alternative Fuels - Engine Controls >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2003 GMC Sierra and 2003 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: DO NOT perform this test if no driveability condition exists. Search for applicable bulletins before proceeding with the diagnosis. DO NOT turn OFF the ignition when performing this diagnostic test. DO NOT clear the DTCs unless the diagnostic instructs you to do so. If there is a condition with the starter system, see appropriate STARTERS article in ENGINES. Ensure the battery is fully charged and the cables are clean and tight. Ensure the PCM and the FICM grounds are clean, tight, and in the proper location. Ensure the CNG and the gasoline fuel tanks are at least 1/2 full.
  1. Install a scan tool. Does the scan tool turn ON? If yes, go to next step. If no, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
  2. Attempt to establish communication with the listed control modules. If you are using a Tech 2, obtain the information with the Class 2 Message Monitor feature:
    • Powertrain Control Module (PCM).
    • Body Control Module (BCM).
    • Instrument Panel Cluster (IPC).
    • Electronic Brake Control Module (EBCM).
    • Driver Information Center (DIC).
    • Heating Ventilation Air Conditioning (HVAC).

    If scan tool communicates with all the listed control modules, go to next step. If scan tool does not communicate with all listed components, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.

  3. Attempt to start the engine. If engine starts and idles, go to next step. If engine does not start and idle, see DTC P1204: VEHICLE DOES NOT START ON CNG  under DIAGNOSTIC TESTS.
  4. Select the DTC display function for the following control modules:
    • The PCM.
    • The BCM.
    • The IPC.
    • The EBCM.
    • The HVAC.

    If scan tool displays any DTCs, go to next step. If no DTCs are displayed, go to step  10.

  5. Using a scan tool, select Captured Info in order to store the powertrain DTC information. When complete, go to next step.
  6. If scan tool displays DTCs which begin with a "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If no "U" codes are displayed, go to next step.
  7. Were any of the PCM DTCs P0601, P0602, or P1621 set? If yes, see DTC P0601-P0607, P1600, P1621, P1627, P1680, P1681, P1683 & P2610: PCM MEMORY under DIAGNOSTIC TEST in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article. If no, go to next step.
  8. If DTC P0611 is set, go to DTC P0611: FUEL INJECTOR CONTROL MODULE PERFORMANCE  under DIAGNOSTIC TESTS. If DTC P0611 is not set, go to next step.
  9. Does the scan tool display DTC P0562, P0563, P1637, or P1638? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article. If no, see DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  10. If vehicle is equipped with the dedicated CNG fuel option (KL8), go to step  12. If vehicle is not equipped with the dedicated CNG fuel option (KL8), go to next step.
  11. Start and idle the engine. Force a switch over to gasoline operation with the scan tool in the Alternative Fuels special functions, output controls menu. If the engine continues to idle, go to next step. If engine does not continue to run, see NO-START - ENGINE CRANKS OKAY under NO-START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES - 4.8L, 5.3L & 6.0L "C", "G", "H", "K", "N" "S" & "T" SERIES - FLEX FUEL & GASOLINE article.
  12. If the customer's concern is with the transmission, see appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSION. If concern is not with the transmission, go to next step.
  13. If the customer's concern is with the Inspection/Maintenance (I/M) testing, see INSPECTION/MAINTENANCE COMPLETE SYSTEM SET PROCEDURE under DRIVE CYCLES in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article. If customer's concern is not with I/M testing, go to next step.
  14. If the customer's concern is a symptom, see SYMPTOMS in TROUBLE SHOOTING - NO CODES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG article. Did you find and correct the condition? If yes, system is okay. If no, see INTERMITTENT CONDITIONS .
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