1998 Mercury Sable SERVICE ENGINE SOON


Computer problem
1998 Mercury Sable 6 cyl Four Wheel Drive Automatic 10 miles

I have had this sable for 2 years when mileage was 110km, and now is 136km, it has been working fine, but last month, the engine service soon light was on, I have my friend checked out, the error code is 401, but the driving is still pretty comfort, and engine is running well, what should I do, if I have it serviced, how much is the parts cost?


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Friday, May 9th, 2008 AT 11:39 PM

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A P0401 Insufficient EGR flow

What does that mean? EGR stands for Exhaust Gas Re-circulation. It is part of the vehicle emmissions system, and is used to reduce combustion temperature and pressure to control Oxides of Nitrogen. There are generally three parts to the EGR system: the EGR valve, an actuator solenoid, and a differential pressure sensor EGR (DPFE). These things work together to deliver the correct amount of recirculation based on engine temperature, load, etc. The P0401 code means that OBD detected an insufficient amount of EGR.

Symptoms you may notice drivability problems such as pinging (a.K.A. Pre-ignition knock) when the engine is under load or the vehicle is at higher speeds. There may also be other symptoms.

CausesA code P0401 most likely means one or more of the following has happened:

The DPFE (differential pressure feedback EGR) sensor is faulty and needs to be replaced
There is a blockage in the EGR (tube), most likely carbon buildup
The EGR valve is faulty
The EGR valve may not be opening due to a lack of vaccuum
Possible Solutions In fixing this code, it is quite common for people to just replace the EGR valve only to have the OBD code return. The EGR valve is not always the culprit.

Use a vacuum pump and pull the EGR valve open while monitoring engine RPM's & DPFE voltage. There should be a noticeable difference in RPM's with the EGR open
Clean out the EGR valve and/or tubing to remove deposits
Check the voltage at the DPFE, compare to specified values (refer to a repair manual for your specific model)
Replace the DPFE sensor (with a good quality / OEM one)
Replace the EGR valve

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Friday, May 9th, 2008 AT 11:48 PM

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