I have a service engine soon light on my 2001 SSE Bonneville. It has been scanned and comes up EGR valve insufficient flow. I have replaced the EGR (twice) and also replaced the M.A.P. sensor upon the advice of a service center. The light still came back on after about a week. What else can I do?

On your EGR tube you have two hoses coming off of it. If you put them on in reverse you will get a code of insufficient flow. I put headers on and replaced EGR tube and valve and the flow sensor and that's the code that I received switched the hoses and solved the code

What code ? are a few different ones for EGR valve > Low & high circuit voltage , testing circuits , PCM testing etc.... no code tells you to replace the EGR valve without testing . Your best bet , take it to a qualified repair shop.
DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient
DTC P0403 Exhaust Gas Recirculation (EGR) Solenoid Control Circuit
DTC P0404 Exhaust Gas Recirculation (EGR) Open Position Performance
DTC P0405 Exhaust Gas Recirculation (EGR) Position Sensor Circuit Low Voltage

Are you sure you have EGR flow?? Hold the EGR valve open the engine should run poorly, if not you have no flow.

If the DTC is P0401 it means that the EGR Valve is clogged or air flow is insufficient.Take EGR valve off and clean carbon out or replace EGR valve with a new one.

It is still safe to drive your car, EGR (Exhaust Gas Recirculation) Valve is clogged or blocked with carbon deposits which is causing your Service Engine Light (SEL) to come on and set a Trouble Code). When you get a chance or when you get back home, have your Mechanic remove the EGR Valve and try to clean it out, or if it is really dirty, it will need to be replaced.

P0401 shows an Exhaust Gas Recirculation Flow Insufficient. Without a good scan-tool you will be playing the "Parts Changing Game". Insufficient flow can be the result of a vacuum leak, bad MAP sensor, an exhaust leak, faulty EBP sensor, carbon build-up, and so on. I wish I could say more but with all the electronics it is more complicated then earlier cars.

You should be fine. Usually what happens is when such a part causes the light to go on, the light will continue to come on again a few time after replacement of the part.

Simply disconnect the battery and let it sit for about 1minute (oat least 30 sec). Then reconnect the battery.

Drive the vehicle and if the light still comes one, take it to an auto parts dealer that can do a diagnostics test and ask them to clear the codes.

Even after this the light may come on - drive for about a week more and if it still stays on, then have the test done again and replace any other part that any codes may present faulty.

Otherwise, sometimes it itakes the computer and engine to adjust to the new part and get an accurate (consistant) reading until the light will stay off.

A lot of the time a light will come on if the O2 sensor(s) are bad. This isnt' a huge issue right aways, will slightly affect feul mileage and the amount of exhaust return into the engine for being reburned. Replace these if necessar (and if affordable).

Please let me know if you need any further assistance.

carsandcomps,

Guru, Premium Expert @ Fixya.com

When you replaced the EGR valve did you check the EGR passage to make sure it wasn't clogged. Since exhaust gasses flow through the EGR passage carbon builds up on the walls restricting flow which can eventually lead to the code p0401 Insufficient EGR flow.

You need to reset the cars cpu,..you can do this by unhooking the negative side of the battery for about 10 minuts,then if the light comes on again,run the obd2 reader again,because there is another problem.

The DPFE (Diferential Pressure Sensor)sensor is usually mounted on the engine and is connected to the pipe that runs from the exhaust manifold to the EGR valve with two rubber hoses. When the sensor goes bad, the Check Engine light comes on and typically sets any or all of teh following fault codes: P0171 & P0174 (lean codes), and/or P0401 (insufficient EGR flow). Nine out of ten times, the fault is not a bad EGR valve or a vacuum leak, but a bad DPFE sensor. A replacement costs about $112 at Ford, or about $48 at an aftermarket auto parts store.I hope this helps.