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Diagnosis & Repair

  1. Connect scan tool to DLC. Start engine and allow to reach normal operating temperature. Operate vehicle while loop status on scan tool indicates CLOSED LOOP. Observe short term Fuel Trim (FT) parameter on scan tool. If display reads -19-0 percent, check for an intermittent problem. See TESTS W/O CODES article. If display reading is not as specified, go to next step.
  2. Inspect air filter and air induction assembly for restrictions. Repair as necessary. If no problems were found, go to next step.
  3. Check scan tool data for proper operation of O2S, MAP and ECT sensors. See SCAN TOOL DATA VALUES table under SCAN TOOL DATA. Repair as necessary. If sensor operation is okay, go to next step.
  4. Turn ignition off. Install fuel pressure gauge. Note fuel pressure with engine running at normal operating temperature. If fuel pressure is between 31-37 psi (2.2-2.6 kg/cm2 ), go to next step. If fuel pressure is not as specified, go to CIRCUIT TEST A2-7A in BASIC TESTING article.
  5. Check Evaporative Emission (EVAP) system for over purging. See FUEL EVAPORATION in SYSTEM/COMPONENT TESTS article. Repair as necessary. If no problems were found, go to next step.
    NOTE: Silicon contamination is identified as white powdery deposits.
  6. Remove and inspect HO2S1 for silicon contamination. Replace HO2S1 if contaminated. Retest system. If HO2S1 is okay, and a rich condition is still present, see BASIC TESTING article or TESTS W/O CODES article.
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