Engine Controls - Description and Operation (Except Diesel & Hybrid): Diagnosis Ford Explorer IV

Pressure Test Point

On some applications there is a pressure test point with a Schrader fitting in the fuel rail that relieves the fuel pressure and measures the fuel injector supply pressure for repair and diagnostic procedures. Before repairing or diagnosing the fuel system, read any WARNING, CAUTION, and HANDLING information. On vehicles not equipped with a Schrader valve, use the Rotunda Fuel Pressure Test Kit 134-R0087 or equivalent.

Low Idle Air Flow Test

When the cold start emission reduction monitor is enabled, the powertrain control module (PCM) commands the idle air control system to increase the RPM, which elevates engine air flow. While this cold start emission reduction elevated air flow is requested, the low idle air flow test compares the measured idle air flow from the mass air flow (MAF) sensor to the commanded idle air control strategy. For the purpose of detecting low air flow concerns, the low air flow test uses the measured air flow and the commanded air flow to create a low air flow index.

Low idle air flow test operation

1. DTC: P050A cold start idle air control system performance
2. Monitor execution: Once per driving cycle, from start up with the cold start emissions reduction active
3. Monitor sequence: none
4. Monitoring duration: 7 seconds

Low idle air flow test entry conditions

1. Engine coolant temperature is between 4.4°C (40°F) and 82.2°C (180°F)
2. Barometric pressure is between 76.2 kPa (22.5 in-Hg) and 105 kPa (31 in-Hg)
3. Engine off soak time is at least 50 minutes
4. Throttle is at closed position

Spark Timing Monitor Test

The PCM is equipped with a spark conduction capture circuit which measures the timing and duration of the spark delivered by processing the flyback voltage signal from the primary side of the ignition coil. When the cold start emission reduction monitor is enabled, the spark control strategy in the PCM commands the spark timing strategy to retard the spark timing. While retarded spark timing is requested, the spark timing monitor compares the measured spark timing from the spark conduction capture circuit to the commanded spark timing from the spark control strategy. For the purpose of detecting spark timing failures, the spark timing monitor increments a fault filter if the measured spark timing is advanced by more than 5 degrees from the commanded spark timing. A failure is indicated if the fault filter exceeds a value of 200, equivalent to a failure duration of approximately 4 seconds.

Spark timing monitor test operation

1. DTC: P050B cold start ignition timing performance
2. Monitor execution: once per driving cycle, from start up with the cold start emission reduction monitor active
3. Monitor sequence: none
4. Monitoring duration: 7 seconds

Spark timing monitor test entry conditions

1. Engine speed is between 400 RPM and 2,000 RPM
2. Engine position and cylinder identification are synchronized
3. There is no concerns with the ignition coils primary circuits