balesray

Found this trouble a couple of places but no for sure solutions. Mileage on truck is 87,453 and is stock all the way. No trouble in the past. Just Oil, filters, tires and battery. Bought new in late 1999. Old and retired but I like my truck and need to fix it soon so help. Replaced the lift pump and filter, checked the APPS voltages and are OK, engine starts quick and idles perfectly. Touch the accelerator pedal and rpm jumps to approx. 1400 and that is all. Foot off pedal, goes back to idle. MIL (engine light) on & all other lights work normal. Wait to start on and times out as usual. Code P1689 is all that reads. HELP PLEASE.