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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 0-19 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 vacuum hoses for leaks, restrictions, or improper routing. Ensure PCV valve and EGR valve operate correctly. Check for exhaust leaks. Check PCM and sensors for proper installation. Ensure ground connections are clean and tight. 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 fuel for excessive water, alcohol, or other contaminants. Repair as necessary. If fuel is okay, go to next step.
  6. Perform CIRCUIT TESTS A2-7C, A2-7D and A2-7E in BASIC TESTING article. Repair or replace as necessary. If no problems are found and lean condition is still present, see BASIC TESTING article or TESTS W/O CODES article below.
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