AN ACR B757 FLC FORGOT TO SELECT THE PROPER RTE IN THEIR FMS DURING A LATE; STEEP DSCNT AND BY THE TIME THEY REMEMBERED; THEY WERE OFF COURSE AND THIS LED TO OTHER PROBS. THEY FINALLY SUCCESSFULLY COMPLETED THEIR APCH MANUALLY.

Narrative

FLYING GLASR 3 ARR MLP TRANSITION. ACTIVE RTE WAS RTE 1 WITH THE GLASR 3 ARR MLP TRANSITION TO ILS RWY 16R TO SEATAC. RTE 2 HAD THE GLASR 3 ARR MLP TRANSITION WITH JAKSN FMS TRANSITION TO RWY 16R TO SEATAC. WE REQUESTED JAKSN FMS TRANSITION WITH ZSE ON 135.52. WE WERE TOLD TO STAND BY. WE WERE GIVEN A DSCNT CLRNC TO CROSS JAKSN AT 12000 FT CLRED JAKSN FMS TRANSITION. THE DSCNT TO 12000 FT WAS GIVEN LATE AND THE FMS SHOWED WE WOULD BE 4000 FT HIGH. I SPD INTERVENED AND INCREASED THE SPD TO 325 KIAS WITH SPD BRAKES DEPLOYED IN ORDER TO MAKE THE 12000 FT AND 250 KIAS XING RESTR AT JAKSN. I WAS CONCENTRATING ON THE DSCNT AND I FAILED TO REQUEST FO TO ACTIVATE RTE 2. AT THE JAKSN INTXN THE ACFT TURNED TO HDG OF 200 DEGS; THE SAME HDG FOR THE JAKSN FMS TRANSITION AND THE GLASR 3 ARR. I WAS CHKING THE APCH CHART FOR THE JAKSN FMS TRANSITION AND IT WAS AT THAT POINT I REALIZED I HAD NOT TOLD FO TO ACTIVATE RTE 2. I TOLD FO TO ACTIVATE RTE 2 AND THE ROUTING SHOWED THE ACFT TO BE SLIGHTLY L OF COURSE. I SELECTED HDG MODE AND TRIED TO CAPTURE THE COURSE. AT THAT POINT I THEN REQUESTED TO MAINTAIN PRESENT HDG TO INTERCEPT THE LOC WHICH WAS APPROVED BY APCH CTL. I ARMED THE LOC AND THE AUTOPLT FAILED TO INTERCEPT SO I DISCONNECTED AUTOPLT AND MANUALLY FLEW. APCH CTL CALLED AS WE HAD GONE THROUGH LOC AND GAVE US A HDG TO INTERCEPT RWY 16R LOC. FACTORS CONTRIBUTING TO NOT ACTIVATING RTE 2. 1) 2 1/2 HR GND DELAY FOR TSTMS IN DTW (FATIGUE). 2) LATE DSCNT CLRNC. 3) 90 DEG INTERCEPT AT 250 KTS.