Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2001CAVALIER LS, 2.4 TREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 59 (ENGINE CONTROL SYSTEM - SELF-DIAGNOSTICS)DIAGNOSTIC TESTSDTC P0171: FUEL TRIM SYSTEM LEANDIAGNOSTIC PROCEDURES
2001 Chevrolet Cavalier LS, 2.4 T
Diagnostic Procedures
2001 Chevrolet Cavalier LS, 2.4 TSECTION Diagnostic Procedures
WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.
- Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM.
- Start engine. Operate vehicle until loop status indicates closed loop. Observe Short Term FT parameter display on scan tool. Is Short Term FT parameter displayed on scan tool less than 20 percent? If yes, see DIAGNOSTIC AIDS . If no, go to next step.
- Visually and physically check for any of the following conditions:
- Splits, kinks, and improper connections in vacuum hoses.
- Correct installation of PCV valve.
- Leaks in exhaust system.
- Start engine. Run engine until engine reaches normal operating temperature. Observe operation of the following sensors at idle, with a scan tool:
- Mass Air Flow (MAF) sensor.
- Engine Coolant Temperature (ECT) sensor.
- Throttle Position (TP) sensor.
- Turn ignition switch to OFF position. Install a fuel pressure gauge. See FUEL GAUGE under FUEL SYSTEMS in REMOVAL & INSTALLATION - 1.8L VIBE article. Observe fuel pressure with engine running at normal operating temperature. Is fuel pressure 44-50 psi (301-347 kPa)? If yes, go to next step. If no, diagnose fuel system. See FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 1.8L VIBE article.
- Check fuel for excessive water, alcohol, or other contaminants. See ALCOHOL/CONTAMINANTS-IN-FUEL DIAGNOSIS in SYSTEM & COMPONENT TESTING - 1.8L VIBE article. Was the fuel contaminated? If yes, go to next step. If no, go to step 8.
- Replace contaminated fuel. After replacement, go to step 10.
- Perform Fuel Injector Balance Test. See FUEL INJECTOR BALANCE TEST WITH SPECIAL TOOL in FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 1.8L VIBE article. Repair or replace as necessary. Was a repair necessary? If yes, go to step 10. If no, go to next step.
- Is a lean condition still present? See SYMPTOM DIAGNOSIS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. If no, go to step 10.
- Use scan tool to clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within CONDITIONS FOR RUNNING DTC . Does DTC run and pass? If yes, go to next step. If no, go to step 2.
- Using scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are displayed, system is okay at this time.
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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.