I was leaving the parking lot at school earlier today when all of a sudden I hear this big *POP* noise... I didn't think much of it until I heard some squealing, so I pulled over and checked under the hood. A loud squealing noise was coming from the timing belt area and the CEL came on... it was a little sluggish until I pulled over and I let it idle a bit and then the squealing noise went away. I checked what code it was throwing and it said 54 ( CKF Sensor (Crankshaft Speed Fluctuation) defective circuit or unplugged / defective sensor ) From what I read in the archives, the sensor is a pain in the *** to get to. What should I do? What was the noise from the belt? You think that the sensor fell off and got snapped off by the belt? My friend said that happened on another friend's B16A... should I just try resetting the ECU and seeing if the CEL comes back? I had my timing belt and water pump changed 2k miles ago... would this have anything to do with it? btw this is for a '97 GSR. Thanks for any help.