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Home >> Chevrolet >> 2000 >> Prizm Base, Automatic, A245E/MS7 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Self-Diagnostics - 1.8L >> Diagnostic Tests >> DTC P0171: Fuel Trim System - Lean >> Diagnostic Procedures

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. Start and warm engine to normal operating temperature. Operate vehicle while scan tool indicates CLOSED LOOP. Using scan tool, monitor short term Fuel Trim (FT) parameter. If fuel trim value is 0-20 percent, see DIAGNOSTIC AIDS  .
  3. Check vacuum hoses for splits, kinks and improper connections. Check PCV valve for proper operation. Check exhaust system for leaks. Check EGR system for proper operation. Repair as necessary. After repairs, go to step  10 . If no problems are found, go to next step.
  4. Start engine and warm to normal operating temperature. Using scan tool, monitor operation of MAP, ECT and TP sensors with engine idling. Check sensors for proper calibration and operation. See SCAN TOOL DATA  under SELF-DIAGNOSTIC SYSTEM. Check vehicle for cause of any erratic sensor readings and repair as necessary. After repairs, go to step  10 . If no problems are found, go to next step.
  5. Turn ignition off. Install fuel pressure gauge. See BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article. Start engine. Observe fuel pressure at idle with engine at normal operating temperature. If fuel pressure is 44-50 psi (3.0-3.5 kg/cm2 ), go to next step. If fuel pressure is not as specified, go to BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
  6. Check fuel for excessive water, alcohol, or other contaminants. If fuel is contaminated, go to next step. If fuel is okay, go to step  8 .
  7. Replace contaminated fuel as necessary. After replacing fuel, go to step  10 .
  8. Perform FUEL INJECTOR COIL TEST - ENGINE COOLANT TEMPERATURE BETWEEN 50-95°F (1.8L) under CIRCUIT TESTS in appropriate SYSTEM & COMPONENT TESTING article. Repair or replace as necessary. After repairs, go to step  10 . If no problems are found, go to next step.
  9. If lean condition is still present, diagnosis by symptom. See appropriate TROUBLE SHOOTING - NO CODES article. If lean condition is not present, go to next step.
  10. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose affected DTC(s).
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