Engine Controls - Tests W/O Codes: Symptoms: Backfire

Check listed items as follows:

• Check Powertrain Control Module (PCM) power and ground circuits. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in SYSTEM & COMPONENT TESTING article.
• Check fuel pressure. See FUEL PRESSURE TEST under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES article.
• Check manifold absolute pressure sensor. See CHECKING MAP SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
• On models with 45RFE transmission, check minimum idle airflow. See CHECKING MINIMUM AIRFLOW under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING article.