Mechanics

ENGINE LIGHT ON

2002 Ford Escape

My 2002 4x4 ford escape engine light is on and staying on. We ran is on the computer and the code p0401 came up. (Exhaust Gas Recirculation Flow Insuffient Detected). What does this mean and how can I fix it?
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Delliott
August 15, 2006.




It could be a bad EGR valve. Seems strange on such a new vehicle, but the trouble shooting for this code is to inspec the EGR valve and piping for obstructions and damaged or bad parts. If nothing is found it calls for doing a test with a scan tool to test the system. I am going to cut and paste the D/O of this code. Try not to have too much fun reading. : Wink: Circuit Description

The PCM tests the EGR system during deceleration by momentarily commanding the EGR valve open while monitoring the Manifold Absolute Pressure (MAP) sensor signal. When the EGR valve is opened, the PCM should see a proportional increase in MAR If the expected increase in MAP is not seen, the PCM notes the amount of error that was detected and adjusts an internal fail counter towards a fail threshold level. When the fail counter exceeds the fail threshold level, the PCM will set DTC P0401. The number of test samples required to accomplish this may vary according to the amount of detected flow error.

Normally, the PCM will only allow one EGR flow test sample to be taken during an ignition cycle. To aid in verifying a repair, the PCM allows twelve test samples during the first ignition cycle following a scan tool Clear Info or a battery disconnect. Between nine and twelve samples should be sufficient for the PCM to determine adequate EGR flow and pass the EGR test if the system is operating correctly.

Conditions for Running the DTC

No Throttle Position (TP) sensor, Vehicle Speed (VSS) sensor, Misfire, IAT sensor, MAP sensor, Idle speed, EGR Pintle Position, ECT sensor, Fuel injector fault(s), Crankshaft Position (CKP) sensor, or MAF sensor DTC(s) set.
Barometric pressure (BARO) is greater than 70 kPa.
Engine coolant temperature is greater than 75 C (167 F).
Intake air temperature is greater than 80 C (176 F).
Engine speed is between 900 RPM and 1400 RPM.
IAC position is steady.
Vehicle speed is greater than 25 MPH.
The throttle is closed.
Commanded state of the A/C relay is steady.
Conditions for Setting the DTC

MAP changes monitored during the EGR flow test indicate insufficient EGR flow.
Action Taken When the DTC Sets

The PCM will illuminate the Malfunction Indicator Lamp (MIL) during the first trip in which the diagnostic test has been run and failed.
The PCM will store conditions which were present when the DTC set as Freeze Frame and Fail Records data.
Conditions for Clearing the MIL/DTC

The PCM will turn the MIL OFF during the third consecutive trip in which the diagnostic has been run and passed.
The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
The DTC can be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed.
Diagnostic Aids

Important: If the EGR valve shows signs of excessive heat, check the exhaust system for blockage (possibly a plugged catalytic converter) using the Restricted Exhaust System Check. See: Diagnosis By Symptom Restricted Exhaust System Check

To verify a repair, clear info with the scan tool and run the EGR flow test keeping the following items in mind: The PCM will only run the EGR flow test during a gradual deceleration.
The PCM will only run the EGR test during a closed throttle condition.
The PCM will only run the EGR test at vehicle speeds above 25 MPH.
Several deceleration cycles will be necessary to run a sufficient number of EGR flow test samples (9-12).
The EGR Test Counter displayed on the scan tool can be useful in determining that the EGR flow test is running and to keep track of the number of test samples taken. The counter will increment each time a test sample is taken.
Check for the following conditions: Vacuum restriction to the MAP sensor. A restriction to the MAP sensor can cause the EGR flow test to fail due to insufficient MAP changes being monitored during the test. Check for objects blocking the vacuum to the MAP sensor. Also check for kinked or pinched MAP sensor vacuum hoses (if equipped.)
Poor connection or damaged harness. Inspect the wiring harness for damage.
If the harness appears to be OK, observe the Actual EGR Position display on the scan tool while moving connectors and wiring harnesses related to the EGR valve. A change in the display will indicate the location of the malfunction.
Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

Tiny
Mikeybdman
Aug 15, 2006.


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