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Home >> Cadillac >> 1996 >> Seville SLS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes >> Diagnostic Trouble Codes >> DTC P0171 - Fuel Trim System Lean Bank 1 >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
  2. Using scan tool, check if any other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If no other DTC(s) are present, go to next step.
  3. Start an warm engine until coolant temperature reaches 185°F (85°C) or greater. Using scan tool, monitor LONG TERM BN. 1 and SHRT. TERM BN. 1 status. If either values are greater than 95-98 percent, go to next step. If either values are less than 95-98 percent, go to step 5).
  4. Using FREEZE FRAME data, note conditions under which the was DTC set. Clear DTC and operate vehicle under the conditions that set DTC. Using scan tool, select NOT RUN SCC and TEST FAIL SCC to verify that this diagnostic test runs while duplicating test conditions. If this diagnostic test ran and failed this ignition cycle, go to next step. If this diagnostic test did not ran or did not fail in this ignition cycle, see DIAGNOSTIC AIDS.
  5. If DTC P0174 is also present, go to next step. If DTC P0174 is not present, go to step 7).
  6. Check vacuum hoses for splits, kinks and proper routing. Check throttle body, air induction system after MAF sensor, intake manifold, PCV and EGR valve for vacuum leaks. Check for contaminated fuel. Ensure PCM grounds are lean and tight. Check for mechanical failure. Repair as necessary. After repairs, go to step 8). If system is okay or no problem is found, see DIAGNOSTIC AIDS.
  7. Inspect bank 1 for exhaust leaks, missing or loose exhaust hardware. Ensure HO2S is securely installed and wiring harness is not touching exhaust or ignition wires. Check for vacuum leaks that will only affect bank 1. Check for mechanical failure. If problem is found, go to next step. If system is okay or no problem is found, see DIAGNOSTIC AIDS.
  8. Repair as necessary. After repairs, verify for proper operation of component(s).
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