Symptom Checks

Perform the following:

• Check power to MAP/BARO sensor. See step 3) of CIRCUIT TEST S in TESTS W/CODES - EEC-IV article in the ENGINE PERFORMANCE section.
• Check ignition system. See IGNITION SYSTEMS in appropriate SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section.
• Check idle speed. See IDLE SPEED in ADJUSTMENTS article in the ENGINE PERFORMANCE section.
• Check Positive Crankcase Ventilation (PCV) system. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section.
• Ensure driveline and transmission are functioning properly.
• Check air intake system. Ensure throttle plate and linkages operate properly.
• Check fuel delivery system. See FUEL SYSTEM in appropriate SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section.
• Check for restricted exhaust system.
• Check EGR system. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section.
• Check Fuel Evaporation (EVAP) system. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section.
• Check engine mechanical condition. Check compression, camshaft, valve train components, etc.
• Check Heated Oxygen Sensor (HO2S) heater. Go to step 21) of CIRCUIT TEST H in TESTS W/CODES - EEC-IV article in the ENGINE PERFORMANCE section.
• Check cooling system (radiator, thermostat, etc.)
• Check customer driving habits (over RPM/speed limiting function enabled).