Guys ... my check engine light came on this weekend on a trip and when I got home I checked for a code(s) ... P0125 came up , which appears to be Insufficient Coolant Temp ( ECT ) for closed loop fuel control . Couple of questions here . Truck runs fine except in neutral at idle and then the rpm hunts somewhat and can go as low as 480 rpm briefly before settling in at 620 rpm . Idle is fine in gear .
I checked coolant level and it`s fine . On a 2003 5.4 Screw , where is the ECT sensor located and is there any way to test it other than removing and replacing ?
How much of a job is it to replace ? The other possibility is the thermostat .... I think .
Comments/help will be appreciated !

Bob

PS ... I got 18.3 mpg running Interstate at 75 to 80 mph with the rear loaded , a 100 lb dog and my lady in it .... I may leave it as is !!! ... just kidding !