Does Ktuner not have a simple on/off display for vtec ? That’s a shame. These ecu need an oil pressure sensor built in.

 

Does Ktuner not have a simple on/off display for vtec ? That’s a shame. Have you had any problems with your speed sensor ? When I got my k24a going I had no vtec as well and that was my issue. The kpro I have wasn’t set up to read the speed sensor and wouldn’t let vtec engage at “0 “ mph.

I'm not sure if they have anything other then the VTS light to show when VTEC engaged. I think the speed sensor is fine. Looking at the first image, it reports my speed just fine from the sensor readings I've selected and it matches my speedometer as well. I have to keep digging to see if the KTuner has an option where it has a toggle to read the speed sensor to ensure it's enabled.

 

I think All the Jdm motors come without the pressure sensor in the vtec solenoid. B series , K series , H etc.

 

That is indeed interesting. I'm curious how it works without one. Learn something new everyday and to think I've been doing this for a while, now 🤪

 

Why do you think vtec isn't engaging? What's your test to verify that it isn't already working as designed?

 

No sound at all when all valves are suppose to open, fuel graph doesn't show indication. I would expect at least crossover engagement sound. I suppose the next test would be to disconnect the exhaust from the catalytic (after the O2 sensor) to see if I can get a more pronounce pitch at crossover

Tuner also says he's not seeing evidence of VTEC engagement

 

I would think it would command more injector
duty cycle as well

 

Have you taken it to the limiter for data purposes ?

 

Yep, I've done a data log at WOT from 2k rpm to the limiter on 3rd gear.

 

I'm now wondering if I disconnect the downpipe from the exhaust manifold, that'll be before both O2 sensors, essentially eliminating both sensors temporarily for this test. Will this be OK or will I get thrown into safe mode, which won't even allow the car to rev past 3k RPM's? What if I separate the cat from the downpipe, which effectively only removes the second O2 sensor but still gets reading from the primary?

Again, I just want to test if I can at least hear VTEC engage

 

Well, the only option I do have is to disconnect from the exhaust manifold because the bolts from the catalytic are rusted and seized. So this will prevent an accurate reading since both O2 sensors, though connected, won't sense proper exhaust

 

Ran the car with disconnected downpipe. No VTEC engagement at all at 4800 rpm (you don't ever hear the engagement/crossover of the additional valves opening up) but my logs show the ECU is at least commanding it. I've tried three solenoids so far so I'm suspecting something electrical at this point. I even went up to about 6k rpm just in case something in the settings is off but the settings in the ECU look good

Before I order an oil pressure gauge to ensure I'm getting proper oil pressure, any way I can test the solenoid and pressure switch?

 

Reviewing the logs, I can see that at the 4800 RPM mark and higher on this first small and gradual pull, the VTP light is still on but no VTS light, which tells me that because of no O2 readings, it's not engaging it or commanding the ECU like I thought it was from my previous last post. You can also see in the column/rows diagram, my ECT look good so the car was up to temperature at that point.

However, on the second gradual pull, I do see the ECU commanding and engaging:

On this third one, I get something again:

Again, on this fourth one, nothing:

Something is definitely up. I can't consistently reproduce. Sometimes it sends signal and sometimes it doesn't but even when it sends signal, I get no real engagement. With open headers/manifold, this should be significantly obvious. To be fair, I just don't know if the CEL complaining about the O2 sensor is causing this.

This was the WOT 3rd gear pull, though with exhaust and O2 sensors fully bolted on:

It's consistent each time sending signal to VTS at 4800 RPM's with everything bolted up so I'm going to say that with open headers, the signal for VTEC engagement is unreliable for sure due to no readings from O2 but like I said, it doesn't engage even when signal is sent.

 

don‘t know for the Ktuner, but on KPro or Doctronic ECUs for the older K20a2, you need a minimum speed for VTEC to engage. VTP also needs to be active for the switch to be triggered. No VSS speed signal, no VTEC. This is until you disable the use of the VSS sensor.
On my K20a2 build, VTP is active from as litte as 3000 rpm. You can log it and it being shown on a graph.

 

Interesting about the VTP needing to be active. On every run, the moment VTS engages, VTP drops off (disables) and when VTS disengages, VTP reactivates (enables). You are saying they both need to be simultaneously active? If so, that's not the case at all from the datalogs. The plot thickens for sure. VSS looks good, though. The datalogs show that it is registering speed signals. What should the minimum speed be set to for VTEC engagement? My understanding is that having the Engage and Disengage Speed set to 0 meant that it doesn't require it to engage VTEC. So, I have it at 0, as you can see from my first post on the 4th image.

Regarding VTP, that's active even at idle (look at my RPM relative to VTP being enabled at idle):

Should the VTP be active only at 3k RPM's or higher and stay on when VTEC is engaged?

 

TPS reading ~20% and no VTEC sounds normal to me, you haven't met the MAP requirement yet. Also, your WOT graph shows TPS only at 80%?

 

This is true even when TPS is maxed at 80%, though. If you look at the other datalogs I've pasted, VTEC doesn't engage at all regardless if it's WOT or partial throttle. I thought WOT was maxed out at 80% anyway?

 

at least for drive by cable throttle cars, TPS % needs to go to 100%.
for the K20a2, VTP needs to be on (triggered by sufficient oil pressure) for the cam switch to happen. If VTP drops the moment VTEC engages, it will disengage again instantly as indicated by the VTS status. VTP is positive at higher rpm at all times as this just indicates sufficient oil pressure for the VTEC mechanism to work.
In KPro you can disable the VTP switch and it will ignore the VTP signal and engage VTEC at any oil pressure.

 

at least for drive by cable throttle cars, TPS % needs to go to 100%.
for the K20a2, VTP needs to be on (triggered by sufficient oil pressure) for the cam switch to happen. If VTP drops the moment VTEC engages, it will disengage again instantly as indicated by the VTS status. VTP is positive at higher rpm at all times as this just indicates sufficient oil pressure for the VTEC mechanism to work.
In KPro you can disable the VTP switch and it will ignore the VTP signal and engage VTEC at any oil pressure.

Thanks for the input. If what you are saying is true, I am not sure how to move forward here. VTP is active even at idle but switches to off the moment VTS is engaged. From your info and pairing that up from what I see in my datalogs, this indicates that the moment VTS engages, I lose appropriate pressure, which is why VTP disengages and I hear no VTEC when VTS engages. I'm also on cable throttle. I'm wondering if there is some calibration that needs to be done for that. My TPS itself is at the right calibration voltage on the throttle body itself. I used a multimeter for this and got it dialed in. Not sure if KTuner requires some additional calibration.

Any suggestions on what I can try next?

 

For what it's worth, I'm also not getting any CEL at all not just for VTEC but for anything. Everything checks out fine. I would expect to throw a CEL at some point if this were an issue. I've checked the Error Codes on KTuner as well as my OBD2 device and both are cleared of any issues. The only CEL I got was when I disconnected the downpipe from the exhaust manifold, which in turn complained about not seeing the O2 sensors.

 

Can I just bypass the pressure switch at this point to see if I can pin-point this? If this is possible, how can I do this? I just recently learned from a previous post on this thread that the JDM engine, which is what I have, doesn't use the pressure switch at all. I'd like to see if this is something I can bypass somehow. If without needing the pressure switch I can get it to engage, I can just get an oil pressure gauge at that point to ensure I always have proper oil pressure at all times

 

Can I just bypass the pressure switch at this point to see if I can pin-point this? If this is possible, how can I do this?

The pressure switch closes with oil pressure. Unplug it then jump the two wires in the connector to bypass.

 

That last log shows a distinctive step in AFR half way through each wot pull. The ktuner is certainly fueling for the high lobe map.

 

Did another run with some logs. This looks better but I still can't hear VTEC at all. I'm going to have to run the open headers again to test but I see more fuel being request this time and both VTS and VTP lights are on simultaneously when VTEC engages at 4800 RPMs. When VTEC is not engaged, only VTP is on, which is what I expect.

The one thing I did was bypass the VTEC pressure switch completely and now I consistently get both VTS and VTP to stay on at 4800 RPMs and above (4800 RPMs is my VTEC engagement point). I'm still not sure about the 80% throttle but I'm checking in the KTuner forums for that.

Here is another look:

 

FYI - 80% WOT is the accurate reading from factory. Confirmed by both my tuner and KTuner themselves.

 

Hooked up a gauge today for oil pressure. I'm getting around 30~ PSI at idle and ramps up while driving. At around 4800 RPMs, I have 80~+ PSI so not an oil pressure issue.

At this point, I'm going to have to pressure test the VTEC assembly, which is a bit more involved and I need to pick up some additional tools for that. This will take me a couple of day's.

 

On the ktuner it's normal behavior for the VTP light to go off when the VTS/vtec gets activated. I also think that your
vtec is engaging. You running the stock intake,cams ect ?

Tune WOT finish set the higher cam angle to 0 degrees and see if the AFR's has changed also check your cam angles that its then using.You could also try and set vtec lower at 4000 to see if theres a change in the AFR graph before the initial 4800 engagement.

With vtec set so high on stock cams which iam assuming it is you might not be able to hear it engage. With the stock oem cams i usually engage vtec at about 3600 to 4000 rpm depending on the setup.

I also think it's kinda impossible to get the fueling right on the car using etuning if the car was not going into vtec.

The tuner will be adjusting the high cam fuel tables from the logs you sent surely he would have picked up if something is wrong. Maybe i am wrong but from what you posted that is my take on it.

 

On the ktuner it's normal behavior for the VTP light to go off when the VTS/vtec gets activated. I also think that your
vtec is engaging. You running the stock intake,cams ect ?

Tune WOT finish set the higher cam angle to 0 degrees and see if the AFR's has changed also check your cam angles that its then using.You could also try and set vtec lower at 4000 to see if theres a change in the AFR graph before the initial 4800 engagement.

With vtec set so high on stock cams which iam assuming it is you might not be able to hear it engage. With the stock oem cams i usually engage vtec at about 3600 to 4000 rpm depending on the setup.

View attachment 105527
View attachment 105528

I also think it's kinda impossible to get the fueling right on the car using etuning if the car was not going into vtec.

The tuner will be adjusting the high cam fuel tables from the logs you sent surely he would have picked up if something is wrong. Maybe i am wrong but from what you posted that is my take on it.

Thanks for the info. I'll share this with my tuner. I hadn't thought about lowering VTEC either. This is indeed stock cams, intake, etc. Everything is stock inside and out including the exhaust and manifold.

My concern is that my tuner also thinks it's not engaging based on the logs I've sent. I also would have expected to hear engagement at open headers but then again the fact that at open headers, I get no O2 reading, it may be causing VTEC not to engage at all so not sure if that was a good test.

When I say you can't hear VTEC at all, I mean just that. Not a dent in sound pitch. I've had stock TSX's in the past that from factory, you can hear engagement so not sure what to think here. Wondering if my catalytic is that clogged or something?

Nevertheless, I'll try the tips you provided because I'm out of ideas at this point for sure. I also didn't know that in KTuner it was normal for the VTP light to go off when VTS engages. I guess I can add that pressure switch back on to the VTEC solenoid assembly.

 

Whewww...this mystery is solved! Here is what I tried:

• Tested continuity on VTEC pressure switch (both sensor connector and wiring)
• Tested continuity on VTEC solenoid (both solenoid connector and wiring)
• Checked oil level
• Checked oil pressure
• Checked VSS
• Checked TPS calibration
• Tested primary and secondary rockers at 42 PSI (per service manual) for each TDC cylinder
• Bypassed VTEC pressure sensor

Those tests above all checked out good. Here is what didn't work and/or added to the confusion:

• Testing with open headers
  • This was a bad test for several reasons. It's before both primary and secondary O2 sensors, which throws a MIL and possibly prevents VTEC from engaging since there are no AFR values being reported to the ECU. I could never get VTEC to engage here but I suspect it was due to the MIL I created when both O2 sensors were bypassed when I disconnected the downpipe from the exhaust manifold
• VTP and VTS indicators in KTuner
  • The fact that the VTP indicator was shutting off when VTS was turning on made it seem like the pressure switch was either sending a bad signal to the ECU or that the pressure switch was bad. I learned that this is how KTuner works for those indicators (thanks @20v_lover for pointing this out and I was also able to confirm after your suggestion)
• 80% TPS at WOT
  • This was confusing because some were saying this should be 100% at WOT. I thought the reading was normal at 80% for this ECU and was able to confirm with KTuner that 80% is the factory reading and this is normal.
• Changed VTEC to 4k RPM engagement with corrective lower/upper limits
  • This didn't make a difference. I still couldn't hear anything

Solution

Since the exhaust and catalytic were rusted shut, I took a leap of faith and just cut the exhaust bolts RIGHT AFTER the catalytic and ran it open this way. Took it for a test drive and I could finally hear a very, very faint/subtle but repeatable sound at VTEC engagement point. Now I know it definitely works. The issue here is that the catalytic seems clogged.

Next steps

• Replace catalytic completely with just a straight runner (now)
• Replace 2" stock exhaust (later in the future)

Thank you all for the assistance on this one

 

So what was the mechanical malfunction? There must be or had been a reading for air flow in/out the engine. Having a clogged catalytic is restriction but has no threshold on the vtec other than flow and AFR but a tune can accommodate for that so I imagine it would be hard to notice the driving performance from the flow restriction. You must have been getting blow by for a while like a leaky oil pan and valve cover gasket leak? How much more information have you gathered since solving the problem and making some improvements? It’s been a while so I want to ask if you might have any updates or added info? I’m asking because I’m still new to k series and k-pro/manager and I’m ago also questioning my vtec but no cat, just resonator and muffler 2.5” piping obd1 kpro v4 on pump and an e85 tune if needed but no flex sensor yet. There is a cel.. the day I bought the car the seller said it was for the o2 because on day of purchase the car only had headers with the o2 at the end so he said it’ll go away with exhaust. Well I have a good flow exhaust and also cut the length of the cai pipe to make it fit and added a filter too! The car has a ktune harness so there’s not that many things that could be going wrong, plus the guy was doing a pretty good job of everything based on what you will find when shopping for someone else’s project that you want to buy and finish because they threw in the flag or what ever. Sorry for a long question on an old post but this was a good post and it’s better to build to this post than to have too many of the same posts with the same questions you know.

 

This is one of the best trouble shoot problem solve threads posted in a long while. Thank you for creating this thread, I am sure it will help others in the future.

 

Thank you kindly!

 

Glad you got it figured out. Stupid cats lol

 

Great news

The ktuner would have thrown an error if there was anything wrong. You could have set vtec very low as well to get a low
oil pressure cell as an additional check but i was fairly confident that it was activating.

 

Great news

The ktuner would have thrown an error if there was anything wrong. You could have set vtec very low as well to get a low
oil pressure cell as an additional check but i was fairly confident that it was activating.

Yep, that's what I figured too but I needed more evidence so I went a bit overboard to ensure it was indeed working. Thanks for the feedback!!

 

first log into your ECU and check the error that causes the CEL.