This is the Acura OBDII code definition for p1381:
You need to check the CKP/CYP sensor(crank position sensor).
It is located under the cam sprocket. To access the timing belt cover need to be removed. Check that connector is good. Also, check that camshaft seal is leaking oil onto the sensor. Disconnect the harness connector and check for 5v at connector with ign. off and key in on position. If 5v present, replace sensor. If 5v absent, you will need to check wiring for short
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That is an generic code definition- the one I gave you is Acura's P01381 code definition. It is from Acura.