The meaning of this engine P1861 Code is found from online and the meaning of the code is p for Powertrain Code Problem is related engine, transmission and emissions systems. 1 for MFG – Manufacturer Specific. 8 for Ignition System Or Misfire. 6 for Control Module Throttle Actuator Position Performance and 1 for TFP Valve Position Switch-Drive Without Drive Ratio. Do not use any wrong meaning of the code what may create more new problems in the car engine. Do not fix the car engine by any person, you should take help from an automobile engineer who has expertise in this matter.