I have a honda p28 with a S300 v3 installed. I DID NOT INSTALL IT. I bought it already put together from HA Motorsports. I have a 94 Honda Civic DX and am using the original engine harness. That means I’ve had to wire in vtec myself using pin A4. I have a fully built GSR swap and I cannot for the love of me get vtex to work. I have given the solenoid direct power, it clicks when the car is off, and when it’s running it will kill the car, which means the solenoid works. I have Vtec enables, the oil pressure disabled, and have disabled the spool error code. I cannot get the ecu to give out the 12v signal needed to pop into vtec. I’ve checked the continuity and everything else I can possibly think of. I have used my friends BRAND NEW p28 S300 v3 on my car and still nothing worked. Does the oil pressure need to be grounded regardless of it being disabled? Anyone got any advice?

 

No, if you have disabled the VTP in the program, it is not necessary to connect the pressure switch to anything. Make sure that your calibration has reachable VTEC requirements, make sure that your VSS is sending a value greater than zero to the ECU (does your speedo work ?). If all of this is good... the problem may be YOUR ENGINE. You may have to check your oil pressure at the cylinder head when VTEC engages to make sure that you have in excess of 50psi at all times from your VTEC crossover point to redline.

 

I just fixed my vtec recently and it was breaking up bad during the vtec engagement and check everything that causes vtec to not engage for 3-4 long as months and found out that changin out my lmas from a recent head I used I know vtec engaged and it fixed my issue.
Not sayin it’ll be the same problem your having but if you checked all you could from the solenoid to electrical and vtec parameters that it needs then it could possibly be worth a shot to change the lmas out.

And as said above hookup an oil pressure gauge and check for pressure, also make sure you check your solenoid screen and clean it out too with brake cleaner.

 

It’s a fully built gsr with brand new skunk2 LMAs, a new solenoid that works, u have an oil pressure guage the reads 60+ during a pull. The screen is nice and clean, and my Speedo works. The engine was a running gsr, so when I put it back together everything went back on. It has the little o ring under cam cap 3 so no internal oil leaks. I’ve tested the outputs if my friends known working s300 and it has a 2 volt output to the vtec at all times and a 14 volt when told to engage. I tired his chip in my ecu, it gave no voltage whatsoever. I tried my chip is his ecu, and it read 2 voltage constantly, no change when told to engage. So I think my p28 is not giving any voltage, although when closely inspected there was no obvious burns or pop anywhere on it. And I think my chip also doesn’t give the voltage like it should, and that also has no obvious issues with it. I refer to the S300 as a chip, just to make typing easier FYI any other suggestions? Should I replace that c14 capacitor? Or that transistor? Should I just wait to send it back to HA Motorsports and see if they can fix it? Thanks

 

If the S300 is still under warranty then email them and explain to them about the vtec problem and see if they can check it out.