Lexus Repair: check engine light came on, toyota service, jp importz

Question
my check engine light came on in my 1997 es300 and the speedometer dropped from 65mph to zero while i was driving on the highway. After that my speedometer just jumps up and down like from 10 to 25 mph and then the car acts as if it doesn't want to go, also sometimes the speedometer will stay at zero and the car will drive with no problem until I hit a bump and the speedometer will begin to jump up and down again. What could this be,I have had the speedometer sensor replaced and a certain mechanic seems to think it's the computer.

Answer
James,
 Take a look at your speed sensor located on the transmission.  If you have access to a scope. You will need to check the wave pattern.
JP Importz
DALLS/PLANO INDEPENDENT LEXUS AND TOYOTA
SERVICE, REPAIR AND PERFORMANCE
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214-221-3135