replace the cluster
Do not rush into doing this (above) A Toyota that is assembled in Japan is far superior to anything UK built - look for the small black sticker on the windscreen at the top driver`s side - the Toyota of Gloucester Main Dealer pointed out this very significant fact.
My car is a 1998 Toyota Corolla GS 3 door hatchback 1332cc with 102k.
My speedo packed in, rev counter fine but within 10 miles the engine management light came on.
My mechanic drove to the nearest scrap yard, bought the c. one foot screw-on speedo extension cable from the gear box end for £5. Sorted for £15.
Apparently the sensor needs feed back on prevailing speed to adjust mixture - hence the engine management light coming on.
PS The sectioned end of the cable sheared, hence lack of drive to speedo proper. Try this first before spending money.