Recommended Procedure:

WARNING: This page does not describe the selected car, but rather 9 other vehicles, including the 2004 Ford RV Cutaway, 2004 Ford Pickup, 2004 Ford F550 Super Duty, 2004 Ford F450 Super Duty, and 2004 Ford Excursion. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: The engine must be at operating temperature.

Connect the scan tool.
Key on, engine running.
Access and monitor the ICP and RPM PIDS.
Operate the engine at low idle speed.

If engine does not stabilize, disconnect the ICP sensor. If low idle speed stabilizes with the ICP sensor disconnected, the problem is most likely in the ICP sensor circuit. GO to PINPOINT TEST Q: INJECTION CONTROL PRESSURE (ICP) SENSOR . If RPM does not stabilize, reconnect the sensor and GO to 12B. INJECTION PRESSURE REGULATOR TEST .