Possible Causes & Corrections

Check the following items:

• Check coolant level. Check cooling system thermostat for proper operation and application.
• Check cooling fan for proper operation.
• Check for restricted airflow to radiator or restricted coolant flow through radiator.
• Check for loose water pump belt.
• Check Knock Sensor (KS) system for no retard.
• Remove spark plugs and check for correct heat range, wear, cracks, wetness, improper gap or heavy deposits.
• Check for incorrect mechanical engine parts such as camshaft, cylinder heads and pistons.
• Check transmission shift pattern and downshift operation.
• Check Transaxle Range (TR) switch input with vehicle in Drive and shifter in Drive or Overdrive.
• Check Torque Converter Clutch (TCC) for proper operation.
• Check Park Neutral Position (PNP) switch circuit. Ensure PNP switch is properly adjusted.
• Ensure initial timing is correct.
• Check PCM grounds. Ensure they are clean, tight and properly located.
• Inspect the items that can cause an engine to run lean long term fuel trim near 24 percent.
• Remove carbon from engine with top engine cleaner.
• Check fuel system for incorrect fuel pressure. Perform BASIC FUEL SYSTEM CHECKS. See FUEL SYSTEMS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
• Check for poor fuel quality and proper octane rating. If scan tool readings are normal and no engine mechanical faults are present, fill fuel tank with a premium fuel and re-evaluate vehicle performance.
• Check for a shifted Engine Coolant Temperature (ECT) sensor. See DIAGNOSTIC TESTS in appropriate SELF-DIAGNOSTICS article.
• If emission test shows excessive NOx emissions, check all systems and components which could cause engine to run lean or too hot.
• Check EGR operation.
• Ensure correct PCM program is installed in vehicle. Check dealer for latest application.