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HOMESERVICE MANUALSCHEVROLET2000CAVALIER BASE, 4D SEDAN, 2.4 TREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS SELF-DIAGNOSTICS - 2.2L & 2.4LDIAGNOSTIC TESTSDTC P0172: FUEL TRIM SYSTEM RICHDIAGNOSTIC PROCEDURES
2000 Chevrolet Cavalier Base, 4D Sedan, 2.4 T

Diagnostic Procedures

2000 Chevrolet Cavalier Base, 4D Sedan, 2.4 TSECTION 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 not greater than - 46 percent, go to next step  5 . If fuel trim index is greater than - 46 percent, go to next step.
  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 greater than - 46 percent, go to step  21 . If fuel trim index is not greater than - 46 percent, go to next step.
  5. Turn ignition off. Check air filter. Replace filter as necessary. After repairs, go to step  21 . If air filter is okay, go to next step.
  6. Check for collapsed or restricted air intake duct. Repair as necessary. After repairs, go to step  21 . If air intake duct is okay, go to next step.
  7. Inspect throttle body inlet from damage of foreign objects that may partially block airflow. Repair as necessary. After repairs, go to step  21 . If no repair is necessary, go to next step.
  8. Inspect throttle body bore, throttle plate and IAC passages for coking and foreign objects. Repair as necessary. After repairs, go to step  21 . If no repair is necessary, go to next step.
  9. Start engine. Ensure all accessories are off. Note idle condition. If idle is low or unstable, go to next step. If idle is okay, go to step  12 .
  10. Using scan tool, check IAC count. If IAC count is less than 100, go to step  12 . If IAC count is not less than 100, go to next step.
  11. Disconnect MAP sensor harness connector. Start and warm engine to normal operating temperature. Ensure system is in closed loop. Using scan tool, select FUEL TRIM INDEX display. If fuel trim index is greater than - 46 percent, go to step  20 . If fuel trim index is not greater than - 46 percent, go to next step.
  12. Turn ignition off. Perform IAC calve performance test, Refer to DTC P0506: IDLE SPEED LOW (2.4L "J" & "N" BODIES)  and DTC P0507: IDLE SPEED HIGH (EXCEPT 2.4L "N" BODY)  or DTC P0507: IDLE SPEED HIGH (2.4L "N" BODY)  . Repair as necessary. After repairs, go to step  21 . If IAC valve is okay, go to next step.
  13. Disconnect fuel pressure regulator vacuum hose. Check vacuum hose for presence of fuel. If fuel is present, replace fuel pressure regulator. After repairs, go to step  21 . If fuel pressure regulator is okay, go to next step.
  14. Turn ignition on, with engine off. Using scan tool, monitor THROT POSITION display while slowly depressing accelerator pedal. If reading increases steadily from minimum voltage to maximum voltage at wide open throttle, go to next step. If reading does not increase steadily from minimum voltage to maximum voltage, go to step  19 .
  15. Diagnose fuel system. See appropriate BASIC DIAGNOSTIC PROCEDURES article. Repair fuel system as necessary. After repairs, go to step  21 . If fuel system is okay, go to next step.
  16. Check fuel evaporation system for proper operation. Ensure canister purge solenoid is functioning properly. See appropriate SYSTEM & COMPONENT TESTING article. Repair as necessary. After repairs, go to step  21 . If fuel evaporation system is functioning properly, go to next step.
  17. Perform injector balance test. See appropriate SYSTEM & COMPONENT TESTING article. Repair as necessary. After repairs, go to step  21 . If no problems are found, go to next step.
  18. Remove and inspect O2S 1 for silicone contamination. If contamination exists, a powdery White deposit on portion of sensor exposed to exhaust system will be present. If silicone contamination is present, locate and repair source of contamination. Replace O2S 1. After repairs, go to step  21 . If no contamination exists, see DIAGNOSTIC AIDS  .
  19. Check TP sensor mounting screws. Tighten or replace screws as necessary. If mounting screws are okay, replace TP sensor. After repairs, go to step  21 .
  20. Replace MAP sensor. After repairs, go to next step.
  21. 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 that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, go to step  2 .
  22. 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.