The P1259 is set when there is a problem in the VTEC Oil Pressure Switch circuit or VTEC Solenoid Valve circuit
Engine Light ON (or Service Engine Soon Warning Light)
P1259 Honda Description
The Variable Valve Timing and Lift Electronic Control (VTEC) system activate the VTEC solenoid valve by the command from the Powertrain Control Module (PCM), and it charges/discharges the hydraulic circuit of the VTEC mechanism that is installed in the valve system to switch valve timing between Low and High. The PCM monitors oil pressure conditions in the hydraulic circuit of the VTEC mechanism according to the VTEC oil pressure switch downstream of the VTEC solenoid valve. If there is a disparity between oil pressure condition in the hydraulic circuit that is determined by the PCM command, and the oil pressure condition that is determined by the status of the VTEC oil pressure switch, the system is considered faulty and the P1259 code is stored.