Really wish I could help. But the PIDs I have are for FORD F150 and would not work for your Honda. Unfortunately assignments (beyond very basic stuff) are not standardized in OBDII. You need to find PIDs for Evap Vapor Management Valve (EVMV) sometimes incorrectly referred to as the Purge Valve, and the Evap Canister Vent Valve, and the Fuel Tank Pressure sensor.

Put simply, the Evap Carbon Canister Vent Valve is Normally Open (via the carbon canister). The EVMV (Purge valve) is Normally Closed. With Key on, Engine Off, Gas Cap on – tank pressure should be = (atmospheric minud nominal resistance of negligible flow through carbon canister via the open Canister vent valve).

Evap test is performed by proportionally ‘modulating’ the EVMV open gradually while monitoring for a decrease in Tank Pressure (via Tank Pressure Sensor). Based on % duty cycle ‘current’ it takes to partially open the Purge Valve, Tank pressure should go negative ONLY so far indicating ‘purge flow’ -via carbon canister- through the Canister Vent Valve (which is Normally Open) into intake manifold. IF NO VACUUM can be generated in the tank – must be ‘gross’ leak or Gas Cap Off.

Your P145C code (Fuel Tank Pressure Sensor Range/Performance Problem) suggests the pressure reading is not a ‘reasonable’ pressure that can be depended upon for these tests (starting out somewhere between atmospheric and – a few inches of water negative). Therefore, It would not be able to determine purge flow rate – or slow leak – or ANYTHING.

Based on this analysis, I believe you need to obtain accurate (OBDII or meter) readings from your fuel tank pressure sensor and ‘verify’ its operation by artificially inducing either pressure or vacuum into the fuel tank – like through the filler neck.

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