Diagnostic Aids

Inspect for the following conditions:

• The Mass Airflow (MAF) is compared to a calculated MAF based upon the Manifold Absolute Pressure (MAP), the Throttle Position (TP), and the engine RPM. A skewed or unresponsive MAP sensor at key ON will cause the predicted airflow value to be inaccurate. Compare the MAP and TP readings to that of a known good vehicle.
• Inspect for a faulty Engine Coolant Temperature (ECT) sensor. Use a scan tool in order to compare the ECT with the Intake Air Temperature (IAT) on a completely cooled engine. The ECT should be within 5°F (3°C) of the IAT.
• For an intermittent condition, diagnose by symptom. See SYMPTOMS (GASOLINE) in TROUBLE SHOOTING - NO CODES - TRUCKS article.