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HOMESERVICE MANUALSCHEVROLET2000CAVALIER BASE, 2D COUPE, AUTOMATIC, 4T40E/MN4REPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS SELF-DIAGNOSTICS - 2.2L & 2.4LDIAGNOSTIC TESTSDTC P0171: FUEL TRIM SYSTEM LEAN (2.4L "N" BODY)DIAGNOSTIC PROCEDURES
2000 Chevrolet Cavalier Base, 2D Coupe, Automatic, 4T40E/MN4

Diagnostic Procedures

2000 Chevrolet Cavalier Base, 2D Coupe, Automatic, 4T40E/MN4SECTION Diagnostic Procedures
  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
  2. If any other DTCs are set, diagnose DTCs as necessary before proceeding. If no other DTCs are set, go to next step.
  3. Start and warm engine to normal operating temperature. Ensure system is in closed-loop. Using scan tool, select FUEL TRIM INDEX. If fuel trim index is less than 32 percent, go to next step. If fuel trim index is not less than 32 percent, go to step  5 .
  4. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. If fuel trim index is less than 32 percent, go to see DIAGNOSTIC AIDS  . If fuel trim index is not less than 32 percent, go to next step.
  5. Check vacuum hoses for splits, kinks and proper routing. Check PCV valve for proper installation. Check for fuel contamination. Check PCM and sensor grounds. Check O2S 1 for correct installation and ensure O2S 1 wiring is not in contact with exhaust manifold. If no problems are found, go to next step. If any problem is found, go to step  7 .
  6. Disconnect MAP sensor harness connector. Operate vehicle in closed-loop while monitoring FUEL INDEX TRIM. If fuel trim index is less than 32 percent, go to step  12 . If fuel trim index is not less than 32 percent, go to step  8 .
  7. Repair fault as necessary. After repairs, operate vehicle in closed-loop while monitoring FUEL INDEX TRIM. If fuel trim index is less than 32 percent, go to step  13 . If fuel trim index is not less than 32 percent, go to next step.
  8. Start and operate engine at idle. Check vacuum for leaks at throttle body, intake manifold and injector "O" rings. Repair as necessary. After repairs, go to step  13 . If no problem is found, go to next step.
  9. Start and operate engine at idle. Using scan tool, check IAC count. If IAC count is greater than 5, go to next step. If IAC count is not greater than 5, go to step  13 .
  10. Perform IAC valve performance test. Refer to DTC P0506: IDLE SPEED LOW (2.4L "J" & "N" BODIES)  and DTC P0507: IDLE SPEED HIGH (2.4L "N" BODY)  . If a problem is found, repair as necessary. After repairs, go to step  13 . If IAC valve is okay, go to next step.
  11. Perform fuel system diagnosis. See FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article. Repair as necessary. After repairs, go to step  13 .
  12. Replace MAP sensor. After repairs, go to next step.
  13. Using scan tool, clear DTCs. Start engine and allow it to idle. Ensure engine is at normal operating temperature. Operate vehicle within conditions required for setting this DTC. Select SPECIFIC DTC function, and then enter this DTC. If scan tool indicates this test ran and passed, go to next step. If scan tool does not indicate this test ran and passed, go to step  2 .
  14. If any other DTCs are set, diagnose DTCs as necessary. If no other DTCs are set, system is okay.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.