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Home >> Chevrolet >> 2001 >> Cavalier LS, 2.2 4 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Self-Diagnostics - 2.2L & 2.4L >> Inspection/Maintenance Procedures >> Inspection/Maintenance System Check (CNG) >> Diagnostic Procedure
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Diagnostic Procedure

CAUTION: Many DTC related repairs will instruct technician to clear DTC information. This procedure will reset ALL I/M System Status indicators to NO and require performing I/M Complete System Set Procedure.
  1. Perform powertrain diagnostic system check for alternative fuel engine controls. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG)  under SELF-DIAGNOSTIC SYSTEM. Repair any DTCs or driveability concerns that may prevent I/M System Status tests from completing. If DTCs or driveability concerns are found and repaired, go to step  3 . If no DTCs or driveability concerns are found and repaired, go to next step.
  2. Check Technical Service Bulletins (TSB) for software updates that may prevent I/M readiness. Perform any reprogramming or repairs indicated by service bulletins. Go to next step.
  3. Using scan tool, monitor I/M System Status display for gasoline control module (PCM). If any tests indicate NO, go to next step. If no tests indicate NO, go to step  6 .
  4. Turn ignition off. Remove CNG fuse (20-amp) from underhood fuse block. Start engine and allow to idle. Using scan tool, verify engine is operating in gasoline mode. Perform necessary set procedures for I/M System Status indicators that were set to NO. Go to next step.
  5. Turn ignition off. Reinstall CNG fuse. Start engine and allow it idle. Using scan tool, verify engine is operating in CNG mode. Perform necessary set procedures for I/M System Status indicators that were set to NO. After performing set procedures, system is okay.
  6. Start engine and allow to idle. Using scan tool, verify engine is operating in CNG mode. Perform necessary set procedures for I/M System Status indicators that were set to NO. After performing set procedures, system is okay.
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