b20ricepower

Hi everyone i am troubleshooting why my vtec isnt working. Ive been doing all the basic checking for continuity and grounds via the helms manual but I noticed something weird. I jumped the vtec oil pressure switch with the ignition on and the engine off and I am getting 12v at the vtec solenoid wire. Not sure if its supposed to get voltage if the engine isnt running. Just for curiosity i re plugged the vtec solenoid back in expecting for the solenoid to click but it didn't. so then I ran a wire straight from the battery to the solenoid and what do ya know it clicks. Why does the solenoid not click on even though its getting 12v via the engine harness? When connected directly to battery it clicks on no problem. Also, is the vtec wire supposed to get 12v with the engine off? I'm confused BTW I am running neptune demon as software if that makes a difference. Also, I am aware of all the possible problems why vtec wouldnt work( clogged screen, low oil pressure, speed sensor, etc etc.) but this seems to be electrical.

b20ricepower

Any one?

turbohatch96y7

iTrader: (15)

Vtec solenoid gets its signal voltage from the ecu. Your either checking the wiring wrong or there's a short in the harness wich I doubt.
Since you applied a positive directly to the solenoid you already ruled out a faulty solenoid.
Check for continuity from the ecu plug to the solenoid plug make sure there isn't any breaks in the wire.
Make sure you have enough oil in the motor, make sure the speeedo is working and check if there is something wrong in the basemap.

turbohatch96y7

iTrader: (15)

And it helps to list specs on the mmotor harness and ecu your using

b20ricepower

Its a chipped vtec ecu obviously. obd1 xenocron chipped with neptune rtp. Settings for vtec in the software are correct. Running a gsr head with blox stg2 cams so vtec crossover should be audible. Continuity from the solenoid wire to ecu is fine. I was just wondering why its getting 12v with the motor not running and if its supposed to or not. Like I said it doesn't click on when connected to the harness only when put straight to battery

turbohatch96y7

iTrader: (15)

seems like you have an attitude for the simple fact of me asking a few questions I'm out, wait for fcm if he wants to help.

0xenocron

You will always read 12v out of the ECU, but the current is so low it cannot click the solenoid over. When the high side driver in the ECU turns on, it releases enough current to drive the VTEC solenoid.

b20ricepower

Ok that explains it. I had a feeling that might be the case but wasn't sure. Perhaps I can hook up a test light to see when and if it activates? I will disable vtec speed check and low load parameters and see if the test light activates while revving. If not then I suppose I can check oil pressure to the cylinder head itself or do the air pressure test.

b20ricepower

Today I ended up taking a quick look at the vtec issue. First I sent the solenoid straight power at about 3500rpm and you can definitely tell that it works so its not getting voltage from the ecu. However it is getting the low amperage its just not receiving the high amperage load to engage. Its a xenocron ecu but I chipped it for vtec.I may have done something incorrectly when doing the vtec conversion kit I suppose

b20ricepower

Any input on how to diagnose why the vtec high current driver isnt working? Or just how to diagnose vtec in the ecu in general?

0xenocron

Are you getting a Code 21 when you do try to cross over into VTEC using the ECU?

b20ricepower

no theres no codes at all which is odd. unless i unplug the sensor or solenoid.

b20ricepower

The way I tested the solenoid is by connecting a test light to the vtec solenoid connector at the solenoid. Then when vtec should activate, the light should glow. I changed all the parameters in neptune so that vtec would engage while reving, but the test light never lit. The problem should be something to do with the high side driver in the ecu but I'm not sure how to diagnose the board, so any input is needed.

Daniel Amayao

The 12v your seeing don’t have enough amp to engage your solenoid, try using a test light instead of a voltmeter and you’ll see that it won’t even light the tester