As the crank position sensor is the buried out the way, you are unlikely to have done anything untoward to it. It is more likely you have disturbed its wiring to the ECU in the loom while doing the valves or removing/refitting the tank - dislodged a connector, trapped or crushed a wire, forgotten to reconnect something etc? I'd pop the tank off and check everything is in order visually, then systematically perform continuity tests.

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