I found this,,,
In the OEM Service Manual error code P1550 is described as O.T.A.S. sensor voltage not plausible.
Possible Cause(s):
Damaged sensor
Damaged circuit wires
Damaged connector or ECU
Open circuit
Service Action:
Check continuity for circuits B-H3, B-H1 and FB-1 ~ FB-5. Refer to Service Manual for locations.