OK first off i know my speed sensor is bad or maybe needs to be rewired since my speedo never leaves 0. My question is when i start the car and drive it operates normally and vtec activates @ 3500. After about 10-15 when its warmed up the check engine light will come on and disengages the vtec(i guess limp mode). If I turn it off n back on vtec will work fine again, can someone give me suggestions as to what could be causing this. I'd appreciate your feedback or personal experience.