Last week my throttle body died on my 1.6 Stilo after a long holiday trip. Halfway the trip the MIL switched on at restart after a short stop, I ignored the lamp and drove home.
At home I hooked on the Examiner and read a fault code P1684 (fault during self learning of throttle body - not plausible). I tried the self learning procedure but the result was "not o.k."
At the second attempt the thottle body was not moving anymore at all - I tried cleaning and lubricating the axle a bit but no reaction of the throttle at all.
As I was not 100% sure if the ECU itself was o.k. I had the car towed to my dealer. They tested the car with a throttle body of another car and it was o.k. so fortunately my ECU was fine.
The dealer ordered a remanufactured throttle body (345 euro incl. VAT) - total costs 396 euro.
The self learning procedure can also be done without an Examiner with Scantool-like interface and Scanmaster software:

send 30-04-07 (start self learning)
wait for 5 seconds -
send 21-7C (procedure check)
read value of 7C - if value is 12 ,self-learning is o.k.

good luck,
Gert

Result of selflearning 12 = decimal so 0C in hex !

Gert

P1684 and P1687. Read the forums and there is a bit of confusion regarding these codes, with some people replacing ECU & Throttle body and checking wiring. Found on two occasions a broken spring in the Throttle body unit being the root cause of these error codes.

Unfortunately, finding a replacement spring is next to impossible so one has to forgo the purchase of a 'NEW' (not reconditioned) throttle-body. Had the misfortune of purchasing a faulty reconditioned 'throttle body', which gave me the impression of the fault being elsewhere. After wasting plenty of time, and ruling out all other systems I was back at to the 'throttle body'.

Hope this post will save people time in diagnosing the P1684 and P1687 DTC's

Broken spring photo below, from a Magneti Marelli C146 Throttle body belonging to a 3 door Stilo 1.6 petrol 2002