I replaced the head cylinder and timing chain assembly a few months ago. Today I noticed my traction light came on randomly. It went away when I restarted the car but back on with bit driving. Shortly after the tachometer would drop to zero with acceleration and then go back up and down randomly. Tach is normal at idle. No stalling. No check engine light until I got it home and turned it on and off a few times. Crankshaft sensor code came up. Had been replaced during timing job. Check wires and everything looks fine. Replaced sensor and no luck. Engine light is still on but the code doesn't come up. Seems like the traction light comes on once the rpms drop to zero.