Hello, Honda-Tech crew!

I have a 1999 Civic SI, and the VTEC system is throwing a code.

I have a question... How does the injectors get the message to adjust the fuel when in VTEC?
The VTEC pressure switch has 2 wires. One to the ECU and the other is a wire from the VTEC pressure switch to the injectors, or injector units ( i cant remember off the top of my head). When VTEC is engaged, does it send the signal down to the injectors and back threw the vtec pressure switch (or vise versa) to adjust the fueling? Or, when in vtec, is the injector pulse controlled totally separate from the pressure switch? (but then, why that wire?)

Ive been getting the P1259 code (VTEC system fault) at random, and now its more consistant. but I can turn off, then on, the car and VTEC will work for a moment, then the code appears again and no vtec, plus the 6.5k rev limit. https://honda-tech.com/forums/images/smilies/mad.gif
I've checked with a volt meter, all the things it tells you to check in the Heines manual, and all reads good. The only one that isnt listed is the wire from the switch plug to the injectors.
also, if the pressure switch is bad, would that only throw a code intermittently? The code will sometimes appear before I exceed 4k rpms, so that hints at electrical. I'm running 10w-30 Mobil1 full synthetic oil too. Idk if that would throw anything off...

I autocross my EM1, and no VTEC and a limiter of 6.5K is pretty frustrating!!

Any advice is a big help! I'll see about checking that wire and maybe a new pressure switch soon, when time and money permit!

 

The no vtec and early rev limit is caused by the ecu going into limp mode. This is a self preservation method for the engine when it senses problems. As far as I know, all fuel enrichment comes from the ecu, nothing else controls the injector so. What were the results of your tests with a voltmeter on the VTeC solenoid?

 

You're wrong about what those two wires do. The switch itself opens up after it sees a certain amount of oil pressure. One wire comes from the ecu, the other goes to ground.

As long as there is enough oil pressure to safely engage the solenoid vtec would normally work. There are a few causes of this code, first is a dent in the oil pan and/or oil pickup, causing too little pressure to the switch, which has a lower threshold than the oil pressure switch. A second cause is the solenoid, for whatever reason, just doesn't work right. Sometimes it will test fine, but people will replace it and the code goes away. Another cause is obviously wiring. Sometimes the solenoid and switch assembly will get all gunked up, normally at the screen.

 

What engine do you have? Was it replaced? When did the problem start? What was the last thing done prior to the problem starting? Any wiring problems that have not be fixed correctly? Are you using a VTEC controller or another ECU?

Verify the contact closing and opening event on the oil pressure switch, and the resistance of the VTEC solenoid. Low oil pressure will cause this code as well. If the wiring or plugs are damaged, inspect them and replace as needed.

For the pressure switch you should have 50PSI of oil pressure at 3000rpm. You can disconnect this sensor and test for the switch open/close event. I don't remember off the top if the switch is normally open or normally closed.

A mechanical VTEC problem will usually produce a misfire, such as if the VTEC solenoid spool valve gets stuck.