Hi Everyone,
2002 Civic EX, 182k miles actually runs great..... when not in limp mode.
Seems I have what looks like a common scenario. Car ran great but I had boiling in the expansion tank when I'd stop.
I replaced the head gasket, temperature gauge is now rock solid. However, shortly after, I started getting P1259 codes and the
car would go into limp mode. To make a long story short, I have removed, cleaned, tested, replaced, everything that I've read regarding this issue, even replaced the oil pump.
I never get the CEL at or near the rpm where vtec would engage. It always happens at a much lower rpm. Cruising down the highway or most commonly
right after startup. I drive a couple hundred yards down the street, stop at a stop sign and get the CEL. Sometimes I clear the code as I'm driving and it comes right
back on, others it will stay off the rest of the trip and run great.
I've been chasing this problem for a month and the weather is started to get cold here. I live in PA. At this point the car is just about useless to me. It's not going
to pass inspection with the CEL and I go up and down hills everywhere here. A 1.7 litre starting out on a hill or going up hill trying to merge into highway traffic at less then 4000 rpm is useless. If I can't use it or it blows up makes no difference.
Seems to be a ton of information regarding bypassing the vtec pressure switch (jumping A4-D6) on previous models. Can't seem to find the same for the D17A2. Does such
a solution exist? I've given up on trying to fix it. Is there no way to just disable vtec so the car won't go into limp mode?
I even thought about just replacing the engine but since I've replaced everything on it, it's possible that its an electrical issue.

Any useful thoughts would be greatly appreciated.

 

Nobody?
I'm out of ideas.

 

Obviously not... your car is still broken. Glossing over the details of EXACTLY what you have done since (and during) the head gasket repair leaves the solution too wide open for anyone to really offer help here. Your frustration with the situation is apparent... that feeling of helplessness really sucks. I get it.

So, please take the time to write it all out so that fresh eyes here can dissect your path of repair and help you find the problem... and ultimately, the fix.

I myself have never been a fan of the VTP wiring hack... and I have never personally seen this work long term. With that said, many people online have claimed success with this wiring modification and trying it is up to you. I have always been concerned with the long-term effects of the voltage passing back to the ECU during VTEC operation. Specifically, can this wiring work-around damage your ECU ? In any case, since the VTP sensors function the same way in your engine as it does in the D16Z6, the solution would be the same process as you have found in the OBD-1 wiring case: Utilizing the A4 VTS and D6 VTP wires in the diagram you have found online would correspond to the B15 VTS and B9 VTP on your chassis wiring at the ECU. Again, I am not endorsing or recommending this repair path, but offer this information to be helpful during your crisis.

 

Thanks for the response JRcivic1.
i will provide details as soon as I have a minute.

 

You will get the P1259 code if your engine oil level is low. Check the oil level.

 

Ok, so here is what I have done.
After receiving the P1259 shortly after replacing the head gasket I did recall some oil draining from the head when I had it off. So, the first thing was to top off the oil. Didn't help.
After this and doing some reading I changed the oil and filter (have done this several times since). Didn't help. I tested the vtec solenoid by applying 12 volts and it worked.
I removed the vtec solenoid valve assembly, cleaned it and the screens and replaced. Didn't work. I replaced the oil pressure switch. Still didn't work. I replaced the solenoid
valve assembly including another oil pressure switch and solenoid. No love. Removed valve cover looked for loose bolts or plugs. uh uh. I removed the head to see if possibly I re-assembled
something correctly during the head gasket replacement that was blocking oil flow. I replaced the oil pump. I wrote the above message crying for help because I was out of ideas.
I have since tried jumpering pins B9-B15 at the ECU. This provided no change. Upon further investigation, I found continuity between these two pins even without the jumper.
That and the fact that there is continuity between the two pins in the oil pressure switch would suggest that the signal is present by default and the pressure switch must open
or "short" the circuit when the proper psi is present. I read where someone had broken the switch while tightening or loosening another bolt. They just put a jumper in the connector
and said everything worked fine. This would cause the switch to be shorted all the time telling the ECU the the oil pressure was correct and that it would only work this way on usdm
cars. So I jumpered the oil switch connector. My CEL light came on in exactly the same place it always comes on. However, I also now got the CEL anytime I get to the rpm that
vtec should engage. Not surprising considering that the switch was unplugged. This does indicate though that the oil pressure switch and wiring is working. The only thing I haven't tried
is jumpering the solenoid wire to the oil pressure switch wire.
The thing is I don't even know if this problem is related to the oil pressure switch at this point. Remember, I start the car I accelerate slightly for several hundred yards then coast to a stop sign. Sometimes I get the CEL
right there. If not, I pull out, again I'm nowhere near vtec engagement rpm and I always get the CEL within 1/2 mile. I usually then let the car get up to normal operating temperature. Then I clear
the codes with my scanner and many/most times the CEL and limp mode will not return for the remainder of my trip. Sometimes the CEL will come right back on 2-3 times, I reset it and then it stays out.
When not on the car runs great. If I start the car and let it just idle in the driveway. I do not get the CEL. I've sat there and let it run for five minutes or more. No light until I leave. So, the ECU must
not test until the throttle is opened or rpms are above idle.
Does the color of the oil pressure switch mean anything? All the ones I recall seeing in the forums and if you pull up the Genuine Honda switch, are green. The one that was originally on my car was white. The one I bought
was white. The one that came with the solenoid valve assembly was black. I'm wondering if the color designates the psi at which the switch activates? Is it possible the switch has a high and low threshold and at startup oil
pressure is too low and if I have the incorrect one its causing the CEL? I find this unlikely given that all during the remainder of the trips, I stop at traffic lights, sit at idle, the car is quiet and oil pressure would be the lowest at
this point and yet the CEL does not come on. I'm grasping at straws now, I know. But like I said above, I'm out of ideas.

Thanks for any thoughts.

Merry Christmas and Happy Holidays to all!

 

Maybe some more help for you in these threads?

https://www.civicforums.com/forums/3...ing-p1259.html
https://www.civicforums.com/forums/3...ent-p1259.html
https://www.civicforums.com/forums/3...-4000-rpm.html
https://www.civicforums.com/forums/3...imited-4k.html
https://www.civicforums.com/forums/3...1259-help.html