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Home >> Chevrolet >> 2001 >> Tracker 2D Utility, 4WD, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics >> Diagnostic Tests >> DTC P0171: Lean Fuel Trim System (2.5L) >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
  2. Start and warm engine to normal operating temperature. Operate vehicle until scan tool indicates CLOSED LOOP. Observe short term FT parameter on scan tool. If scan tool displays less than 15 percent, go to next step. If scan tool does not display less than 15 percent, go to step  4 .
  3. Turn ignition on, with engine off. Using scan tool, clear DTC information function. Operate vehicle within FREEZE FRAME conditions that set DTC. Observe the total fuel trim parameter on scan tool. If scan tool displays less than 33 percent, see DIAGNOSTIC AIDS  . If scan tool does not display less than 33 percent, go to next step.
  4. Turn ignition off. Visually and physically check for any splits, kinks, and improper connections in vacuum hoses. Check for proper PCV valve operation. Check for exhaust system leaks near the HO2S. Check for correct operation of EVAP control system. Repair as necessary. If a problem is found, go to step  11 . If no problem is found, go to next step.
  5. Start and warm engine to normal operating temperatures. Operate engine at idle. Using scan tool, observe operation of MAP, ECT and TP sensors. Compare the observed sensor readings with the typical scan tool data values. See appropriate PIDS VALUE CHARTS article. Repair as necessary. After repairs, go to step  11 . If no problem is found, go to next step.
  6. Turn ignition off. Install Fuel Pressure Gage (J-34730-1A). Start engine. Observe fuel pressure with engine idling at normal operating temperatures. If fuel pressure is 39-45 psi (270-310 kPa), go to next step. If fuel pressure is not 39-45 psi (270-310 kPa), diagnose fuel system.
  7. Turn ignition off. Check fuel for excessive water, alcohol or other contaminants. If contamination is found, go to next step. If no contamination is found, go to step  9 .
  8. Replace any contaminated fuel. After replacing fuel, go to step  11 .
  9. Check fuel injectors for even and normal discharge. Fuel should be dispersed in a conical spray pattern. Check fuel injector resistance. See appropriate SYSTEM & COMPONENT TESTING article. If no problem is found, see DIAGNOSTIC AIDS  . If problem is found, go to next step.
  10. Replace faulty fuel injectors. After repairs, go to next step.
  11. Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and operate vehicle within the conditions for running this DTC or until DTC diagnostic test has run. See CODE ENABLE CRITERIA  . If DTC runs and passes, go to next step. If DTC resets, go to step  2 .
  12. Turn ignition on, with engine off. Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS  . If no DTCs are displayed, system is okay.
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