hey man, saw one of your post a few years ago with a similar issue on an honda civic, however mine is motor D16Y9 and the ECU is P2K and i cant seem to find a proper diagram about it and I KNOW the wiring must be different, because i been testing everything and its there, just in different places, but anyways
My issue is the code 14, refering to IACV issues, at first it had both code 19 and code 14, the 19 refering to A/T and thats where it clicked that my ride must have had a previous swap and thus had an open circuit where the solenoid was, i put on some resistances and voila, the code 19 went off but 14 remained - the symptons BEFORE cleaning was that it was stuck at 1500RPM (pretty much just like the older post i saw in which you helped the guy out) but after i cleaned the IACV and the throttle body the thing not only got stuck at 1500 but also was unstable (i'll be attaching videos and also a picture of the older post i saw of you)
After inspecting the old IACV it was busted as fuck, so i bought and placed a new one and it improved stopping the unstable RPMs, however the code was still popping and it was still stuck at 1500RPMs, if i unplug the IACV while the motor is on it gets down to about a 1000RPMs, i tried resetting the ECU and the code pops AS SOON AS I TURN ON THE SWITCH (as in, not even turning on the motor) so i assumed it was an electric issue and started testing the resistances and what not...
turns out i do have continuity between the ECU and the IACV pin outs (its 3 pinned IACV), doing some discussion with the AI it says that as long as the ECU and the motor were originally A/T it should be a form of turning off the "Check engine light" so i been trying my best at testing every single thing, at one point i disconnected the ECU "A" connector to test stuff, plugged it back in, and the code went away (i said EUREKA!) however, after i tried turning on the whole engine, the motor tried to keep 1000RPMs for a few seconds, then turned on the Check engine light and went back to 1500RPMs...
Cleaned all the body ground joints, made sure things were plugged in, moved the little screw to try and control the RPMs manually, checked for vacuum leaks of which there is none (since i try to stop the airflow in the little hole of the IACV and the motor shuts down, or revs down if i just stop it a little) and now, heres where im at right now
I BEEN TRYING TO FIGURE OUT, if in the IACV connector (the one that goes from my ECU to the thing in the throttle body) should be giving me VOLTAGE ON THE SIDE PINS, the middle one gives 12V, which is normal... But cant seem to find if its normal for the side ones (negative and positive IACV switches according to the diagram you posted) should be giving ANY voltage at all, one gives me 12V, and the other gives me sometimes 10, i test again, gives me 11V... I dont think they should be sending voltage right? I once read that if they are sending out voltage it means theres a busted fuse INSIDE the ECU, however im afraid of bringing down the whole thing, just want to try and run out all of my "fix outside" options before turning to an electrician to help me figure out the ECU
ADDITIONAL INFO - Motor model: D16Y9 (no Vtec) - ECU: 37820-P2K-V51 - My main language is spanish but i master the english language so ignore anything said in the videos lol, we can do a videocall if you want too i have no issue
things i already checked (and regulated if needed)
- TPS voltage
- Throttle physical position (it had a lot of opening left by the previous owner)
- Changed the IACV (tested it works, it has 20ohms of resistance on both sides too and the motor reacts if you disconnect it as expected)
- Closed out the circuit for the A/T and thus erasing code 19
- Cleaned all if not most of the body grounds
- Thru the IACV doesnt run any of the coolant hoses because where i live is not needed, we stay at around 34°C ambient or room temp, so the cars come without them but it shouldnt be an issue plus we checked for any vacuum leak from there and theres none
- All possible Vacuum leaks were throughly tested, all negative
- let me know if you need anything else
This will be a short legend of the order i placed the photos and videos in case the title doesnt show when it upload them!
1. Codes 14 and 19 are on, the 19 was deleted once i did the A/T thingy
2. Engine unstable idle, plus it gets stuck
3. Engine unstable idle AFTER cleaning, slightly better
4. Engine no longer unstable but stuck at 1500RPM after changing IACV
5. Code 14 NOT SHOWING after doing the tests of continuity between ECU and everything else (essentially unplugging and plugging it back in)
6. First time turning the engine on after code 14 not showing, different behaviour, wanted to keep 1000RPM, then turned it on and went back to 1500RPM
IMAGES
7. ECU "A" connector, 26 pins
8. ECU version
9. ECU side with the pins where the connector A goes
10. my IACV connector
11 Code 19 solution, it closes the circuit for the A/T and it no longer showed up
My issue is the code 14, refering to IACV issues, at first it had both code 19 and code 14, the 19 refering to A/T and thats where it clicked that my ride must have had a previous swap and thus had an open circuit where the solenoid was, i put on some resistances and voila, the code 19 went off but 14 remained - the symptons BEFORE cleaning was that it was stuck at 1500RPM (pretty much just like the older post i saw in which you helped the guy out) but after i cleaned the IACV and the throttle body the thing not only got stuck at 1500 but also was unstable (i'll be attaching videos and also a picture of the older post i saw of you)
After inspecting the old IACV it was busted as fuck, so i bought and placed a new one and it improved stopping the unstable RPMs, however the code was still popping and it was still stuck at 1500RPMs, if i unplug the IACV while the motor is on it gets down to about a 1000RPMs, i tried resetting the ECU and the code pops AS SOON AS I TURN ON THE SWITCH (as in, not even turning on the motor) so i assumed it was an electric issue and started testing the resistances and what not...
turns out i do have continuity between the ECU and the IACV pin outs (its 3 pinned IACV), doing some discussion with the AI it says that as long as the ECU and the motor were originally A/T it should be a form of turning off the "Check engine light" so i been trying my best at testing every single thing, at one point i disconnected the ECU "A" connector to test stuff, plugged it back in, and the code went away (i said EUREKA!) however, after i tried turning on the whole engine, the motor tried to keep 1000RPMs for a few seconds, then turned on the Check engine light and went back to 1500RPMs...
Cleaned all the body ground joints, made sure things were plugged in, moved the little screw to try and control the RPMs manually, checked for vacuum leaks of which there is none (since i try to stop the airflow in the little hole of the IACV and the motor shuts down, or revs down if i just stop it a little) and now, heres where im at right now
I BEEN TRYING TO FIGURE OUT, if in the IACV connector (the one that goes from my ECU to the thing in the throttle body) should be giving me VOLTAGE ON THE SIDE PINS, the middle one gives 12V, which is normal... But cant seem to find if its normal for the side ones (negative and positive IACV switches according to the diagram you posted) should be giving ANY voltage at all, one gives me 12V, and the other gives me sometimes 10, i test again, gives me 11V... I dont think they should be sending voltage right? I once read that if they are sending out voltage it means theres a busted fuse INSIDE the ECU, however im afraid of bringing down the whole thing, just want to try and run out all of my "fix outside" options before turning to an electrician to help me figure out the ECU
ADDITIONAL INFO - Motor model: D16Y9 (no Vtec) - ECU: 37820-P2K-V51 - My main language is spanish but i master the english language so ignore anything said in the videos lol, we can do a videocall if you want too i have no issue
things i already checked (and regulated if needed)
- TPS voltage
- Throttle physical position (it had a lot of opening left by the previous owner)
- Changed the IACV (tested it works, it has 20ohms of resistance on both sides too and the motor reacts if you disconnect it as expected)
- Closed out the circuit for the A/T and thus erasing code 19
- Cleaned all if not most of the body grounds
- Thru the IACV doesnt run any of the coolant hoses because where i live is not needed, we stay at around 34°C ambient or room temp, so the cars come without them but it shouldnt be an issue plus we checked for any vacuum leak from there and theres none
- All possible Vacuum leaks were throughly tested, all negative
- let me know if you need anything else
This will be a short legend of the order i placed the photos and videos in case the title doesnt show when it upload them!
1. Codes 14 and 19 are on, the 19 was deleted once i did the A/T thingy
2. Engine unstable idle, plus it gets stuck
3. Engine unstable idle AFTER cleaning, slightly better
4. Engine no longer unstable but stuck at 1500RPM after changing IACV
5. Code 14 NOT SHOWING after doing the tests of continuity between ECU and everything else (essentially unplugging and plugging it back in)
6. First time turning the engine on after code 14 not showing, different behaviour, wanted to keep 1000RPM, then turned it on and went back to 1500RPM
IMAGES
7. ECU "A" connector, 26 pins
8. ECU version
9. ECU side with the pins where the connector A goes
10. my IACV connector
11 Code 19 solution, it closes the circuit for the A/T and it no longer showed up
Images & Videos (Click to enlarge)
Aug 12, 2026 at 9:01 PM
