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Powertrain Control Module Systems Diagnostic System Check (2.2L - Bi-Fuel)

WARNING: This page is about a different car, the 2002 Pontiac Sunfire, 2002 Chevrolet Cavalier, 2001 Pontiac Sunfire, and 2001 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION: Search for applicable Technical Service Bulletins (TSBs) before proceeding with diagnosis.
CAUTION: Ensure both fuel tanks are at least 1/4 full. Do not clear DTCs unless instructed by a diagnostic procedure.
  1. Turn ignition switch to LOCK position. Connect scan tool to Data Link Connector (DLC). DLC is located on left side of instrument panel, near steering column. Turn ignition switch to RUN position. If Malfunction Indicator Light (MIL) is illuminated, go to next step. If MIL is not illuminated, diagnose and repair MIL concern. See SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. For 2002, see SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
  2. Using scan tool, attempt to establish communication and retrieve data from Powertrain Control Module (PCM). If scan tool displays PCM data, go to next step. If scan tool does not power up, go to TEST A: SCAN TOOL DOES NOT POWER UP  under SYSTEM TESTS. If scan tool does not display PCM data, go to TEST B: SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE  .
  3. Using scan tool, attempt to establish communication and retrieve data from Alternative Fuels Engine Control Unit (AF ECU). If scan tool displays alternative fuels data, go to next step. If scan tool does not display alternative fuels data, repair ignition relay circuit. See SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. For 2002, see SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
  4. Using scan tool, check PCM and AF ECU for stored DTCs. Record and store DTC FREEZE FRAME and FAILURE RECORDS information if applicable. If no DTCs are stored, go to next step. If any DTCs are stored, go to step  10 .
  5. Using scan tool, command MIL OFF utilizing scan tool ENGINE OUTPUT (GASOLINE) for MIL. If MIL turns off, go to next step. If MIL does not turn off, repair MIL circuit. See ANALOG INSTRUMENT PANELS article. For 2002, see ANALOG INSTRUMENT PANELS article.
  6. Crank engine for at least 10 seconds. If engine starts, go to next step. If engine does not start, go to step  9 .
  7. Determine which fuel system engine is operating on by observing fuel indicator light and scan tool NGO ENABLE INPUT and OUTPUT parameters. If vehicle is operating on alternative fuel and NGO ENABLE INPUT and OUTPUT parameters indicate same data, go to next step. If vehicle is operating on gasoline and fuel indicator light is not illuminated, and NGO ENABLE INPUT and OUTPUT parameters do not indicate same data, diagnosis and repair concern. See SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. For 2002, see SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
  8. Operate vehicle and observe and record engine data parameters. Compare engine data on scan tool with ENGINE SCAN TOOL DATA LIST. If engine data values are normal or within typical range, go to step  11 . If engine data values are not normal or not within typical range, diagnose and repair concern. See SELF-DIAGNOSTICS article in ENGINE PERFORMANCE for applicable DTC diagnosis. For 2002, see SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
  9. Remove CNG fuse (20-amp) from underhood fuse block. Crank engine for at least 10 seconds. If engine starts and runs with CNG fuse removed, diagnose and repair ignition relay circuit. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If engine does not start with CNG fuse removed, perform diagnostic system test in SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. For 2002, see SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
  10. Compare stored PCM DTCs to stored AF ECU DTCs. Diagnose DTCs in following order:
    • If a DTC is stored only in PCM, diagnose and repair concern. See SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. For 2002, see SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
    • If a DTC is stored in both modules or only in AF ECU, diagnose and repair concern. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
    • If different multiple DTCs are set, diagnose and repair PCM DTCs first.
    After all DTCs have been diagnosed and repaired, go to step  15 .
  11. If vehicle has a driveability symptom, go to next step. If vehicle does not have a driveability symptom, go to step  13 .
  12. Perform fuel system diagnosis and return to this step. See BASIC DIAGNOSTIC PROCEDURES article in ENGINE PERFORMANCE. For 2002, go to BASIC DIAGNOSTIC PROCEDURES article in ENGINE PERFORMANCE. If fuel system diagnosis located concern and concern is now repaired, go to step  15 . If fuel system diagnosis did not locate concern and concern is not repaired, repair concern by symptom. See appropriate TROUBLE SHOOTING - NO CODES article in ENGINE PERFORMANCE.
  13. If there is not a fuel gauge, fuel gauge selector or fuel indicator light operation concern, go to next step. If there is a fuel gauge, fuel gauge selector switch or fuel indicator light operation concern, diagnose and repair concern as necessary. See ANALOG INSTRUMENT PANELS article. For 2002, see ANALOG INSTRUMENT PANELS article.
  14. Ensure ignition switch is in LOCK position. Remove CNG fuse (20-amp) from underhood fuse block in order to force a switch over to gasoline operation. Crank engine for at least 10 seconds. If engine starts and runs on gasoline with CNG fuse removed, go to next step. If engine does not start and run on gasoline with CNG fuse removed, diagnose and repair alternative fuel pump relay circuit.
  15. Disconnect all test equipment except scan tool. Connect any disconnected components. Replace CNG fuse. Using scan tool, clear AF ECU and PCM DTC information. Turn ignition switch to LOCK position and wait 30 seconds. Start engine and operate vehicle. If DTC was set, ensure vehicle is operated to allow DTC to test. Observe fuel indicator light and MIL. Observe vehicle performance and driveability. After operating vehicle, inspect both control modules for DTCs. If vehicle operates on alternative fuels with normal driveability, and fuel indicator light or MIL does not illuminate and no codes are stored, system is okay at this time. If vehicle does not operate on alternative fuels with normal driveability, or fuel indicator light and/or MIL illuminates and codes are stored, go to step  1 .
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