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Home >> Isuzu >> 1999 >> Trooper Part Time >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Trouble Code Identification >> DTC P0175: Bank 2 System Too Rich >> Diagnostic Aids

Diagnostic Aids

An intermittent may be caused by a poor connection, rubbed-through wire insulation or a broken wire inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection, and damaged harness. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

  1. Perform On-Board Diagnostic (OBD) System Check. See BASIC DIAGNOSTIC PROCEDURES article. Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. Go to next step.
  2. If any DTCs other than P0172 and P0175 are set, diagnose them first before proceeding. If no other DTCs are set, go to next step.
  3. Operate vehicle in closed loop mode while using scan tool to read BANK 1 L.T. FUEL TRIM values. If values are not as specified, go to next step. If L.T. FUEL TRIM value is less than -15 percent for A/T and is less than -12 percent for M/T, go to step  5.
  4. Using scan tool, read and record FAIL RECORDS data. Clear DTCs and operate vehicle within FAILURE RECORDS conditions. If DTC P0175 is set, go to next step. If DTC P0175 is not set, check for an intermittent problem. See DIAGNOSTIC AIDS .
  5. If DTC P0172 is also set, go to next step. If DTC P0172 is not set, go to step  15.
  6. Check air filter element condition. Replace air filter element if necessary. Retest system. If air filter element is okay, go to next step.
  7. Check for collapsed or restricted air intake duct. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
  8. Check MAF inlet screen for blockage or foreign objects which may partially block airflow sample through MAF sensor. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
  9. Start engine. If a high or unsteady idle condition exists, go to next step. If Idle is okay, go to step  11.
  10. Turn ignition off. Check throttle body bore and throttle plate for restriction or foreign objects. Check for clogged IAC passages. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
  11. Disconnect vacuum hose from fuel pressure regulator and check it for presence of fuel. If fuel is present, replace fuel pressure regulator. Retest system. If no fuel is present, go to next step.
  12. Turn ignition on. Using scan tool, read TP ANGLE while slowly depressing accelerator pedal. If TP ANGLE increases steadily from zero percent at closed throttle to 100 percent at wide open throttle, go to next step. If TP ANGLE does not increase as specified, go to step  19.
  13. Disconnect MAF sensor connector. Operate vehicle in closed loop mode while monitoring scan tool BANK 1 L.T. and BANK 1 S.T. FUEL TRIM. If both FUEL TRIM values decrease to about zero percent, go to step  20. If FUEL TRIM values do not decrease to about zero percent, go to next step.
  14. Perform FUEL SYSTEM PRESSURE TEST. See BASIC DIAGNOSTIC PROCEDURES article. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
  15. Turn ignition on. Connect test light between canister purge solenoid connector terminals. If test light comes on, go to next step. If test light does not come on, replace PCM. Retest system.
  16. Using an ohmmeter, check for continuity to ground in Red/Blue wire between PCM connector "A" terminal No. 15 and canister purge solenoid connector. See PIN VOLTAGE CHARTS. If continuity exists, repair short to ground. Retest system. If continuity to ground does not exist, go to next step.
  17. Perform injector balance test. See FUEL SYSTEM in SYSTEM & COMPONENT TESTING article. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
  18. Remove HO2S No. 1 and check for silicone contamination (powdery white deposit). If HO2S No. 1 is contaminated, replace HO2S No. 1. Retest system. If HO2S No. 1 is not contaminated, check for an intermittent problem. See DIAGNOSTIC AIDS .
  19. Check for loose TP sensor mounting screws. Adjust TP sensor if necessary. If mounting screws are tight, replace TP sensor. Retest system.
  20. Replace MAF sensor. Retest system.
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