Now I'm not exactly sure to even think because I have never owned a car with Traction Control...but every once in a while just randomly (it seems to me) the TRAC OFF light comes on which according to the manual means something is wrong...but then if it stays on for a few miles/minutes every time the transmission upshifts it shifts really hard and makes a kind of clunk noise......

Note: I have a 4-spd auto in a 01 Z24

Check fluid level?




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make sure your IAT sensor is in place, you might need to get a new one