Symptom Checks

Check the following items:

• Check the following Parameter Identification (PID) values: DPFEGR, ECT, IAC, LONGFT 1, LONGFT 2, VPWR and VREF. See appropriate article:

For 4.2L Pickup, see PIN VOLTAGE CHARTS - 4.2L .

For 4.6L Pickup, see PIN VOLTAGE CHARTS - 4.6L .

For 5.4L Pickup, see PIN VOLTAGE CHARTS - 5.4L .

For 4.2L & 4.6L Van, see PIN VOLTAGE CHARTS - 4.2L & 4.6L .

For 5.4L Van, see PIN VOLTAGE CHARTS - 5.4L GASOLINE .

For 6.8L Van, see PIN VOLTAGE CHARTS - 6.8L .

• Check secondary ignition system. See CIRCUIT TEST JB in appropriate article:

For 4.2L Van, see TESTS W/CODES - 4.2L .

For 4.6L Van, see TESTS W/CODES - 4.6L .

For 5.4L Van, see TESTS W/CODES - 5.4L GASOLINE .

For 6.8L Van, see TESTS W/CODES - 6.8L .

For 4.2L Pickup, see TESTS W/CODES - 4.2L .

For 4.6L Pickup, see TESTS W/CODES - 4.6L .

For 5.4L Pickup, see TESTS W/CODES - 5.4L GASOLINE .

• Check fuel delivery system. See CIRCUIT TEST HC in appropriate TESTS W/CODES article.
• Check exhaust system. See CIRCUIT TEST HF in appropriate article:

For 4.2L Van, see TESTS W/CODES - 4.2L .

For 4.6L Van, see TESTS W/CODES - 4.6L .

For 5.4L Van, see TESTS W/CODES - 5.4L GASOLINE .

For 6.8L Van, see TESTS W/CODES - 6.8L .

For 4.2L Pickup, see TESTS W/CODES - 4.2L .

For 4.6L Pickup, see TESTS W/CODES - 4.6L .

For 5.4L Pickup, see TESTS W/CODES - 5.4L GASOLINE .

• Check PCV system. See CIRCUIT TEST HG in appropriate TESTS W/CODES article.
• Check engine mechanical condition. Check intake manifold gasket, camshaft and valves.
• Check for contaminated Mass Airflow (MAF) sensor.
• Ensure engine operates at normal operating temperature.
• Ensure transmission operates properly.
• Check for dragging brakes.