P1259: A problem in the VTEC OIL Pressure Switch circuit or VTEC Solenoid Valve circuit.

First, unplug the 2 pin connector on the VTEC pressure switch. Check for continuity with a multimeter, if there is no continuity at the pressure switch, replace it.

If there is continuity, turn the ignition on and check Pin 2 of the pressure switch wiring harness. It's a BLU/BLK wire on the bottom half of the connector. You should get around 12V when grounded. If there isn't 12V, check the wiring harness for an open or short to ground.

If there is voltage, measure voltage between the 2 pins in the connector. There should also be the same voltage. If not, check the wiring and ground connection for an open.

Check the VTEC solenoid resistance to ground. Should be 14-30Ω. If not, replace the VTEC solenoid.

If both the VTEC solenoid and the VTEC pressure switch and respective wiring are fine, the remaining diagnosis involves checking oil pressure at the solenoid and then the PCM.

It will probably be the VTEC solenoid, the screens are known to clog on them.



http://www.6thgenaccord.com/forums/s...ighlight=p1259

Unbelievable from a decent home mechanic...
 

Well, I really appreciate your guys help with this. At first I thought it could have been my clutch (never having any clutch issues yet owned all MT Hondas, I didn't know if it was slipping or not). I found my issue (and yet a stupid one).

Thank you Jim for saying something about the oil pressure. I went and bought a 3593 filter and put my car up, drained out the oil, and unscrewed the filter I had installed on accident (the 3506). After further investigation, get this, the o-ring from my older yet filter (one before the 3506) had come off and was stuck on the seal area. The o-ring fit perfectly inside the O-ring of the 3506 filter making the gasket seal not 1/4 of an inch like usual, but almost 1/2 an inch all the way around, which restricted the ports in the filter (fewer ports in the 3506 filter than a 3593 filter to begin with) causing my oil pressure to be out of wack (i'm sure coupled by the absence of the relief valve). So, I replaced the oil filter, got her all buttoned up, let her warm up to driving conditions, and I could not get the issue to duplicate.

Two valuable lessons were learned:
1. ALWAYS make sure you grab the correct part number, even though they are in the same stack, someone could have mixed em.
2. ALWAYS make sure you have all the old parts out when replacing with new parts.

Many thanks again as I could have had a pretty costly list of time/money chasing this issue down when all it was was a bonehead mistake. After checking my RPM's history with my car chip, the only time I hit above 3500RPM was a couple days ago and I changed my oil about 3 weeks ago, hence why i never had an issue before.

Now to figure out the P0420 issue, which my chip is now checking O2 sensor voltage to see if any of those are out first...:)

Thank you again,
James

P0420 simply means your cat is out. If you like, a pair of HELP! 18mm Spark Plug Non-Fouler adapters can make that code go away for about $10 and 15 minutes of your time.

http://www.honda-tech.com/showthread.php?t=1841240

you know, that's odd... my car does the same thing sometimes at 4k rpms as well... but once i turn the car off, i wait 30min and then use it again nothing happens... i actually thought it was like a "defense mechanism" of the car that went on when it misfired or something. now im a bit concerned... i'll check the vtec solenoid...

I'm pretty sure in your 1999 car the rear O2 sensor does absolutely nothing for engine/fuel control. All it does is measure whether the catalyst is working OK, and that (rear) sensor would be responsible for setting P0420.

Oil filters... I've got the habit of opening the box. I bought a Mobil-1 oil filter once & when I got it home I opened the box to find a FRAM. Not even the right FRAM number...!