Is it a V6 or a 4cyl?
What makes you think its bad?
Have you checked the oil lately? low oil can cause this code. Check it and make sure its full first.
There is a resistance test. Disconnect the connector for the Vtec solenoid. At the Vtec oil pressure switch disconnect it.
Check for continuity between both pins of the switch. If there isnt than the switch is bad. If there is continuity than turn the key on and measure voltage at the Blue/Black wire and ground at the Vtec pressure switch connector and ground. If there isnt the vtec pressure switch is bad.
If there is 12 volts than go ahead and measure voltage accross the 2 pins at the Vtec pressure switches connector(harness side) If there isnt than isnt its possible its a bad PCM.
If there is voltage turn the ignition off. Disconnect the solenoids connector and measure for continuity between the wire that goes to the solenoid and ground. There should be between 14-30 Ohms. If there isnt than the Vtec solenoid is bad.
If there is between 14-30 Ohms. than we are goung to have to measure oil pressure.
Let me know if this helps or if you need more info.
What didnt work?
where did you conclude with the tests.
Did you check the oil level yet?
You could remove the vtec solenoid and there is a screen. Check to see if there is any debris in the screen. If there is clean it and try again. If not i would replace the vtec solenoid and the switch
Was it happening before you put it in?
I was going off of the code p1259 that you told me you have. Did the check engine light come on before or after you put the rail in?
Ok well from her on in is where it gets difficult. Basically we need to watch the oil pressure. But in order to do that we need a special "Y" fitting. The Y goes where the pressure switch was and the gauge and the switch screw into it. Now we need a scanner. Basically what we are looking for is at low RPM the switch will be on and the Vtec solenoid will be off. once the perameters are met the two will switch.
To be honnest. What i would do is clear the code and drive the car. See if you can get it to recode. If a P1259 comes back than i would replace the entire valve assly and the switch.
Doesnt really matter which gauge you use as long as there is a "Y block that both the switch and the gauge can screw into.