Service Engine soon light

I have a 2000 Expedition with approx. 114,000 miles on it. Everything is working great, except a few weeks ago, my service engine soon light came on. It stayed on for a few days, then went off. It was off for several days and then came back on for a day. Any ideas what it could be?

Thanks,
Christina

O2 sensor and DPFE (EGR pressure) sensors are the most common.

I see they have redesigned the DPFE (again).

you have a bad sparkplug and or coil pack for that sparkplug.there are 8 coil packs in all ,chances are you will foul a sparkplug again if you don't change the coil pack directly above the fouled plug.(also change boot)
then reset your ser. eng. light by removing the neg. battery cable from battery for 30 seconds.

I am betting on the O2Sensor..
If it was the(coil pack/spark plug wire/spark plug ) - When you start the car, in the morning it will run rough, until the computer compensates for the bad coil pack/spark plug wire/spark plug..
Just my 2Cs..

I had this problem. Mine turned out to be a fuel vapor recirc problem. Old gas cap was venting vapor, popping a code. New cap=no SSS light. Cheap fix, if thats your problem.

1999 Ford Expedition XLT 4.6L
2003 Volvo S80 2.9L

[exphilly]

Had same problem. Would not pass inspection. Dealer said it needed new vapor sensor and vapor sol. Cost 480.00 Buddy said try new gas cap. Give him a cigar. Fixed problem.

2001 expy xlt 4.6

[paulg928]

when the light is on go to auto zone thay will tell you why the light is on