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Home >> Pontiac >> 2001 >> Aztek Base, AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Self-Diagnostics >> Diagnostic Tests >> DTC P0172: Fuel Trim System - Rich >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
  2. Using scan tool, recheck for DTCs. If any DTCs are set, other than P0172, diagnose affected DTCs first. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no other DTCs are set, start operate engine at idle and warm to normal operating temperature. Ensure engine is operating in closed-loop. Using scan tool, record the Long Term Fuel Trim data. Turn engine off. Turn ignition on, with engine off. Review FREEZE FRAME/FAILURE RECORDS and record displayed data for this DTC. If scan tool indicates that long term fuel trim is less than -13 percent, go to next step. If long term fuel trim is not less than -13 percent, see DIAGNOSTIC AIDS .
  3. Operate engine at idle. Using scan tool, observe HO2S parameters. If values are within 200-800 millivolts and fluctuating, go to next step. If values are not within 200-800 millivolts and fluctuating, go to step  5.
  4. Turn engine off. Check MAF sensor inlet screen for blockage. Check vacuum hoses for splits, kinks and proper connections. Check for collapsed or restricted air intake duct. Check dirty or restricted air filter or for objects blocking throttle body. Repair as necessary. After repairs, go to step  7. If no problem is found, go to step  6.
  5. Turn engine off. Check HO2S for proper installation. Ensure harness connectors and wires are secured and not contacting exhaust system. Repair as necessary. After repairs, go to next step. If no problem is found, diagnose fuel system. See BASIC FUEL SYSTEM CHECKS (GASOLINE) in appropriate BASIC DIAGNOSTICS PROCEDURES article.
  6. Check for excessive fuel in crankcase. Check evaporative emissions control system. Check fuel pressure regulator for proper operation. Ensure all injectors are functioning properly. Repair as necessary. After repairs, go to next step. If no problem is found, diagnose engine for mechanical problem.
  7. After repairs, use scan tool to reset the Long Term Fuel Trim, then clear DTCs. Turn ignition off for 30 seconds. Operate vehicle within the conditions for running this DTC. See CODE ENABLE CRITERIA . If DTC runs and passes, go to next step. If DTC resets, go to step  2.
  8. Using scan tool, observe 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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