Ford sport trac 2009 service engine light is on. Don't know what is triggering it.

SOURCE: 2007 FORD EXPLORER SPORT TRAC 4X4 Change oil light on

Press and hold the SELECT/RESET
control switch to select SYSTEM
CHECK when “SYSTEM CHECK /
HOLD RESET” is displayed in the
message center. Selecting this
function from the SETUP MENU
causes the message center to cycle through each of the systems being
monitored. For each of the monitored systems, the message center will
indicate either an OK message or a warning message for two seconds.
Pressing the SELECT/RESET control switch cycles the message center
through each of the systems being monitored.

The sequence of the system check report and how it appears in the
message center is as follows:
1. OIL LIFE RESET
2. CHARGING SYSTEM
3. WASHER FLUID
4. DOOR AJAR
5. EXTERIOR LAMP
6. BRAKE SYSTEM
7. PARK BRAKE
8. MILES TO EMPTY
9. FUEL LEVEL LOW (will only display if 50 miles or less to empty)
To reset the oil monitoring system to 100% after each oil change
[approximately 5,000 miles (8,000 km) or 180 days] perform the
following:
1. Enter SYSTEM CHECK to display
“OIL XXX% RESET IF NEW”.
2. Press SELECT/RESET control
switch to display “HOLD RESET IF
NEW OIL”.
3. Press and hold the
SELECT/RESET control switch for
more than 2 seconds. Oil life is set
to 100% and “OIL CHANGE SET TO
100%” is displayed.

SOURCE: Ball joint replacement-2003 Ford Sport Trac

if you dont have a ball joint press and dont know how to use one then dont do it, but if you do its not that bad of a job just jack the truck up under the control arm remove the brake rotor then take the lower ball joint nut off then use a pickle fork to break the ball joint loose then take the axle nut off push the axle out of the bearing and use the ball joint press to remove and replace the ball joint

SOURCE: service engine soon/ABS/Trac lights are staying on

Have the ABS codes scanned. This will get you started in the right direction. Possibility is that one or more of the wheel speed sensors is not working or intermittent - could be wiring or connectors on these as well. Another possibility is the EBCM, Electronic Brake Control Module. I believe the EBCM will throw 1216 code in many cases. THese can be rebuilt online for about $150.00.
The more likely problem is the wheel speed sensors. THese are an integral part of the wheel hub. About $100.00 each for the part. About $250.00 each to have them replaced. They can be tested with an AC voltmeter by spinning the wheel. Also, they should read roughly 850 ohms resistance. The ABS codes will tell you which ones are not reporting.

SOURCE: how to replace fuel filter on 2001 ford sport trac

Buy a manual and read it. The manual will tell you how to replace...

SOURCE: how do i reset the check engine light on my 2003

Unplug the battery for about 10 min then plug it back up start the engine. the computer should reset, if the light comes back on then u still have problems.