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Home >> Chevrolet >> 1996 >> Blazer 4D Utility, AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - 4.3L >> Diagnostic Trouble Codes >> DTC P0174 - Fuel Trim System Lean Bank 2 >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform ON-Board Diagnostic (OBD) System Check. Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. Go to next step.
  2. Check exhaust system for corrosion, loose or missing hardware. Ensure HO2S is installed securely, and connector and harness are not contacting exhaust manifold or ignition wires. Check vacuum hoses for splits, kinks and proper routing. Check throttle body, intake manifold, and EGR valve for vacuum leaks. Check IAC, if high or unsteady idle condition exists. Check crankcase ventilation valve, spring and "O" ring for proper installation. Check for fuel contamination. Check for good VCM and sensor grounds. If any of these items isolate or require repair, go to step 8). If all items are okay, go to next step.
  3. Cautiously connect a fuel pressure gauge to fuel rail. Turn ignition off for 10 seconds. Turn A/C off. Turn ignition on, engine off (fuel pump should run for about 2 seconds). Cycle ignition off and on until maximum pressure is obtained. Note fuel pressure while pump is running (pressure may vary slightly when pump stops). If pressure holds at 60-66 psi (4.2-4.6 kg/cm2 ), go to next step. If pressure is not as specified, go to step 11).
  4. Start engine and allow it to idle. If pressure drops 3-10 psi (0.2-0.7 kg/cm2 ), go to next step. If pressure does not drop as specified, go to step 11).
  5. Perform A-7, INJECTOR BALANCE TEST under FUEL SYSTEM in appropriate SYSTEM/COMPONENT TESTS article. If an injector problem is found, go to step 9). If injectors are okay, go to next step.
  6. Perform CANISTER PURGE SOLENOID CHECK under EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM/COMPONENT TESTS article. If a solenoid problem is found, go to next step. If solenoid is okay, go to DIAGNOSTIC AIDS.
  7. Repair EVAP system. Operate vehicle in closed loop mode while using scan tool to read LT and ST fuel trim values. LT fuel trim value should decrease to less than 158, ST fuel trim value should decrease to less than 180. If fuel trim values are as specified, go to step 10). If values are not as specified, go to DIAGNOSTIC AIDS.
  8. Repair items as necessary. Operate vehicle in closed loop mode while using scan tool to read LT and ST fuel trim values. LT fuel trim value should decrease to less than 158, ST fuel trim value should decrease to less than 180. If fuel trim values are as specified, go to step 10). If values are not as specified, go to step 3).
  9. Replace fuel injector(s) as necessary. Operate vehicle in closed loop mode while using scan tool to read LT and ST fuel trim values. LT fuel trim value should decrease to less than 158, ST fuel trim value should decrease to less than 180. If fuel trim values are as specified, go to next step. If values are not as specified, go to step 6).
  10. Lean condition does not exist. If driveability problem still exists, see appropriate TESTS W/O CODES article.
  11. See A-6, FUEL SYSTEM DIAGNOSIS under BASIC FUEL SYSTEM CHECKS in appropriate BASIC TESTING article.
  12. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter DTC P0174. Operate vehicle within conditions required to set DTC. If scan tool displays RAN AND PASSED, go to next step. If scan tool does not display RAN AND PASSED, return to step 2).
  13. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.
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