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Home >> Buick >> 1996 >> Roadmaster Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control Systems - Tests W/Codes >> Diagnostic Trouble Codes >> DTC P0172 - Fuel Trim System Rich Bank 1 >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
    NOTE: If other DTC(s) are present, except P0175, diagnose affected DTC(s) first.
  2. Start and warm engine to normal operating temperature. Ensure system is in "closed loop" operation. Using scan tool, select FUEL TRIM DATA LIST and monitor LT FT AVG. BN 1 and ST FT AVG. BN 1 values. If LT FT AVG. is greater than -14 percent and ST FT AVG. reads greater than -10 percent, go to next step. If not greater than specification, go to step 4).
  3. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME and/or FAILURE RECORDS data and note parameters. Turn ignition off for about 15 seconds. Start engine and operate vehicle within the conditions required for this diagnostic to run, and as close to conditions recorded in FREEZE FRAME/FAILURE RECORDS as possible. Select DTC function then enter DTC which was set. If scan tool indicates that this test failed this ignition, go to next step. If scan tool does not indicate that this test failed this ignition, see DIAGNOSTIC AIDS.
  4. If DTC P0175 is also present, go to next step. If DTC P0175 is not present, go to step 6).
  5. Check for collapsed air intake duct, restricted fuel filter, improperly installed MAF sensor, foreign objects in MAF sensor inlet or for fuel in fuel regulator hose. Repair as necessary. After repairs, go to step 7). If components are okay, or repair was not necessary, diagnose fuel system. See SYSTEM/COMPONENT TESTS article.
  6. Check for leaking fuel injector(s) in bank 1. Repair or replace as necessary. After repairs, go to step 9). If injector(s) are okay, go to step 8).
  7. Replace or repair affected components. After repairs, go to step 9).
  8. Replace faulty HO2S. After replacing oxygen sensor, go to next step.
  9. Using scan tool, select DTC, CLEAR INFO function. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter DTC P0172. Operate vehicle within the conditions that set the 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, repeat step 2).
  10. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTC(s) are displayed, diagnose affected DTC(s).
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