I haven't got a code yet. It was probably 40 miles since the the speedo behaved funny. How long it will throw a code for VSS related issue?

I know I should check before ask further question. But, for the worst part, if the speedo is really broken, can I get any year CSVT speedo to work?

98 Silver Frost E0 SVT. 1011/6535. DOB 05/16/97 Owned since new. Optimized y-pipe. Bosal Exhaust w/ silencer inserts. K&N intake w/ MAF. Ford Racing 9mm wires. 05 Saab 9-2X Aero Satin Grey. Cobbs Accessport Stage 2.