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VCM disable - a new and better way

634K views 2K replies 398 participants last post by  verbatim 
#1 ·
relatively new to this forum, but not new to reading the threads here. I have read almost all the posts on the VCM vibration issue and for those that aren't familiar with it, please do a search and do some reading as I don't plan to recap everything.

My opinions and experience are this: I don't like VCM at all. I am one of those that are experiencing vibrations and that's why I came to this forum in the first place. I have always been of the opinion that equipment is meant to be run, and when it's not, bad things happen. Cylinders in an engine are meant to be firing at all times and when they're not, you get oil bypassing, plug fouling, misfiring, vibration, and all the bad things that each of these conditions leads to. Adding active engine mounts and noise cancelling technology is just adding more crap to try and hide a bad condition. It is an initiative to help save 1 mpg and is more of a gimmick to satisfy EPA regulations etc. It's bad for engines as can be seen by all the complaints here and with every automaker that tries this.

My original intent was to try everything people here do to get rid of the vibration, pcm updates, engine mounts, spark plugs, etc etc... then I realized I needed to focus on disabling this B.S. system instead.

I tried disconnecting the rear bank oil pressure switch as is recommended by many. It did indeed disable VCM, however it was accompanied by the CEL indications, DTC's. As well, I live in a cold, snowy, icy climate and when I did this, after a short time of driving, the VTM-4 light came on in the dash and I noticed immediately that I had much less traction. The vehicle became a 2wd vehicle. At every start from a stop on a slippery surface, the front end slid to the side and there was not the usual amount of traction. It was painfully obvious that VTM-4 was also disabled. this was unacceptable to me. I need 4wd and I couldn't live with the CEL codes. If you like a 2WD vehicle and warnings all over your dash, by all means use this method. If you want something better, read on.

As most of you know, VCM doesn't engage until the engine is up to operating temperature. According to my OBD II device, it kicks in at around 167 degrees. This is where I decided to focus my attention. After doing some research on the ECT sensor, I went out and bought a 1K potentiometer. I drove my pilot until it was at operating temp and then I stopped and pulled ECT 1 sensor wire. I put the pot inline with the sensor, then started the engine and using the OBD II reader, I dialed the pot until the engine temp read 165 degrees. I went for a test drive and there were no CEL lights and the VCM never engaged. It was heavenly to drive the vehicle with VTM working, no CEL codes, and no VCM. It was how this vehicle should drive.

Now know what some of you are thinking. What if the engine overheats? I'll never know. Well, my plan is this. I'm going to install a switch and an aftermarket digital coolant gauge with audible alarm. So, what I'll do is run the vehicle up to operating temperature in the normal position so that if the engine needs the ECT reading to adjust anything, it can. then \I'll flick the switch and VCM will be off and the potentiometer will be sending a signal that the engine is at 165F to the PCM. that's less than ten degrees below operating temp and shouldn't cause any problems. I certainly didn't see any when I was driving. I also will have the aftermarket sensor monitoring engine temp, and giving an alarm if it overheats.

The only thing I'm unsure of at this point is whether the radiator fans will come on in hot weather as usual. I believe they will because I'm pretty sure they use ECT 2 as the input for this. I'll find out I guess.

I plan on making it look like a very professional installation, using one of the blank spots next to the DTS switch to install my switch. Not sure exactly where the aftermarket gauge will go yet. I've ordered the OEM female connector to make a harness so that I don't have to cut any wires and I can put it back to original with no evidence. The male half of the connector is going to be a bit more difficult as it isn't sold individually and so I'm going to try to hack apart an IAT sensor to make one.

For those that are interested in this, I will post updates of my progress with pictures. I just thought I'd share what I found so far.

Cheers,
 
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#36 · (Edited)
This was already posted on the other VCM thread, but I'm posting here also just for the sake of completeness for this thread. Took my pilot in this morning. I told them about the vibration issue and the groaning noise with the A/C. I gave them the Honda TSB numbers when I brought it in. They just called me back and they already replaced the power steering pump for the groaning noise and they've ordered the propeller shaft for me. All fixed under warranty, no arguments, no questions asked. It couldn't have been more painless.

As I've preached numerous times, I'm not a fan at all of VCM and I did this just to get the updated parts. I'm disabling VCM tomorrow morning again. I only did this so that it doesn't vibrate as much if someone test drives it later down the road when I want to sell it.

Note also that they did not mention any diagnostic codes! My own code reader showed that there were no permanent or stored codes from when I was swapping my harness out, but now this is confirmation that if you do get that code for the first couple drives, (it then goes away), the stored code can be cleared simply by disconnecting the battery like I did. Now that I know to only swap it out when the engine is cold, that's not even an issue anymore. I've swapped it out four times now with the engine completely cold and it returns no errors.
 
#37 ·
verbatim, are you by chance using a scangauge to read the codes and monitor the water temp? Have you tried clearing the code with the reader vs pulling the battery cable? I'm not exactly in a hot climate but I'm going to try out your fix in a few weeks.
 
#45 · (Edited)
No, I'm using a transmitter I bought off ebay coupled with an app on my smartphone calle DashCommand. It reads codes fine and has a "clear diagnostic codes" function, but it seems to do nothing, so that's why I cleared it by disconnecting the battery instead. Again, this is moot now since installing the harness when the engine is cold results in no CEL codes at all.

If you're set on periodically disconnecting & reconnecting the VCM system and want to do it remotely without opening the hood. Why not wire in a DPDT switch..... sensor harness leads in the center, wiring to the original sensor on one throw and the fixed resistor on the other? Space on the lower left side for additional switches......could even do a TPDT switch and control a separate LED circuit to indicate when it is connected/disconnected.
I have no intention of switching VCM on and off. It's going to be off permanently. The only reason I've been disconnecting it so far is to try different methods to stop the CEL errors from coming up, which I have now solved, and also to revert to stock before taking to the dealer like I did yesterday. I don't want to install anything that isn't easily removable when it's time to take it in. If others wish to do this, fill your boots.

Here is what I have made and is currently installed on my Pilot. The resistor is under the heat shrink tubing. The two pigtail leads are solid resistor leads and fit perfectly into the oem female HVG connector. I wrap that end in duct tape after I insert the leads into the connector, then I plug the female connector of my harness into ECT1. Works like a charm. If enough people are interested, I'll buy the 100 connectors from China and make it professional looking, otherwise, I'll just run it as is.
 

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#39 ·
Verbatim, I'm digging into the adding the 40 ohm series resistor on ECT1 and have a couple more questions. I don't have the shop manual so please bear with me.

I found a decent source for a female pigtail at: Honda acura IAT ECT Vtec connector plug pigtail civic element fit pilot accord For Sale - DVAutoParts.com

I unplugged the connector at ECT1 and it looks identical to the one shown at that link. I also found some sources from China as you had mentioned but they require a 100-500 minimum order quantity.

For the male connector, like you noted, it's much harder to find. Have you considered getting an ECT1 sensor and dissecting it to remove the series R but leave the internal electrical leads? You could then mount it in a watertight box/tube with it's existing threaded fitting along with the 40 ohm series R and the female connector pigtail hanging out the other side. The side with the flexible pigtail plugs into the existing ECT1 sensor near the EGR valve and the male connector bolted to the box/tube plugs into the existing wire harness. What do ya thinK? How did you prototype the series resistor fix on your vehicle? I'm trying to avoid cutting the factor wiring harness.
 
#41 ·
That fits the older pilot but not the new pilot. That's an HX connector you need a HV or HVG. Secondly, that's a female connector. I have no problem buying those in small quantities. I found the female HVG connector and have five at home that I bought. It's the male connector that's the problem that I need to buy min 100 from China. I've looked everywhere so if you or anyone else can find it somewhere else, I'd appreciate it. But I doubt you will. I'll post a picture of it later. The one in your link for earlier pilots I can also find quite easily along with the male half.

I've landed on a resistor value of 68 Ohms (1/2 watt rating although this is likely overkill). This seems to work best for keeping the engine temp low enough in all cases from what I've tested, so if anyone is trying this themselves, go with that value. Readily available at you local electronics supply store.

You will not be able to do this mod without at least the female connector which as I mentioned is readily available. Without it, you will have to splice into the factory wires. Something I refused to do... For the other end, I just have soldered solid resistor leads onto my pigtails and these insert perfectly into the female connector for now then I wrap it in duct tape. Once I have the male connectors, it'll be truly plug and play.

WIll post more later and a pic. Have to run home, plumbing emergency.
 
#42 ·
You're right, that's the right connector for 2012, but that won't fit the pigtail harness you linked to. Look carefully, the slots are orientated differently.

Oh, and you'll need a crimping tool, the terminal and wire seals and the retainer. You can get these from cycleterminal.com
 
#44 · (Edited)
The first one is the one I'm sourcing from china. Min quantity 100. The links you posted don't work but it's the only one on Alibaba and that's the guy I'm using.

The female I can get from him too, but I can buy in lower quantities from other places.

Virtually everything from Alibaba is from China or overseas.
 
#46 ·
verbatim... I AM IN!

If you have to buy a 100 of the connectors, how much money are we talking about?

What if you could get 5 to 10 people together and split the cost of the connectors and the other parts needed. About how much money are we talking about? This way you would have a bunch of connectors for people in the future, so you could recoup your cost and some of your time.

Who knows maybe this mod will be popular with people that buy a 2016 Pilot
 
#50 ·
Hi Mr Mom -I live up in northern OH, about 30 miles from the lake. The fix that verbatim is working on will be pretty easy to install once it is all completed. I'll call it the "VCM Defeater" for now. You just unplug the connector from the engine coolant temp sensor 1, plug the VCM defeater into that same coolant temperature sensor, and then plug the original connector that went to the coolant temp. sensor into the other end of the VCM defeater. The only tool you need is a screwdriver to pop off that large black plastic cover on top of the engine. The coolant temperature sensor is under there. See the earlier pic I posted for the location. Total time to install VCM defeater is about 5 minutes.
 
#51 · (Edited)
Hi Mr Mom -I live up in northern OH, about 30 miles from the lake. The fix that verbatim is working on will be pretty easy to install once it is all completed. I'll call it the "VCM Defeater" for now. You just unplug the connector from the engine coolant temp sensor 1, plug the VCM defeater into that same coolant temperature sensor, and then plug the original connector that went to the coolant temp. sensor into the other end of the VCM defeater. The only tool you need is a screwdriver to pop off that large black plastic cover on top of the engine. The coolant temperature sensor is under there. See the earlier pic I posted for the location. Total time to install VCM defeater is about 5 minutes.

Thanks!

I did read the thread, but get glazed over when the tech talk starts in. I'll re-read.
 
#52 ·
I wouldn't leave it installed when taking it in. There's no way it should void a warranty but somebody might just use it as an excuse to.

It won't hurt your vehicle. Keep an eye on the new gauge position (only slightly lower). That's the new normal.

I've ran it this way for weeks. No indication of anything bad. Just drives the way it should. My gf took it on a 9 hour round trip to the mountains yesterday to go snowboarding. Not a lick of a problem and she got 21 mpg without trying. If she would have drove it easier and not idled it waiting for others she would have got higher.

If you're really queasy about it then don't do it. I firmly believe it does zero harm and is actually good for the engine but you should be convinced too or you'll always be worried.

The guy from China said he's back next week. I'll take the chance and put in the order. If it makes some folks happier with their ride, it's worth it to me.
 
#62 ·
verbatim, I hooked up the scangauge to get some temperature readings and to compare them against your readings. ECO mode doesn't get enabled until the coolant temperature reaches 166-167 deg. F. And the normal operating temperature of the coolant is 170-175 deg. F. I checked this over a few days where the ambient temperature varied from ~15-35 deg. F and the heater temp was set to 71 deg. F. Do those coolant temps agree with your readings before you added the series resistor?

I also noticed that, if it's cold enough and I crank up the heater to maximum, the coolant temperature will start dropping and ECO mode gets disabled around 161 deg. F. It seems there is some hysteresis between 161 and 166-167 deg. F and the heater temperature setting could affect the optimal value for the resistor. If you wanted to go crazy with the fix, you could use a digital pot. whose value gets adjusted based on the coolant temperature. A microcontroller runs the show and uses the true coolant temperature as feedback to adjust the pot. and send the corrected temperature back to the PCM. When the coolant temp. is close to the ECO disable threshold, not much resistance correction is needed. But when the coolant temp. is hotter, more correction is applied.

If anybody lives in a cold climate and they want to temporarily disable VCM, set your heater to maximum, sweat like crazy, and enjoy the smooth ride. :29:
 
#68 ·
I got the same readings and documented this some time ago. Your assessment is correct as you'll have to vary the resistor to keep it in the 161-167 range as the actual engine temp fluctuates. In Fl, I see 182 coolant temps (A/C off) so you'll need to have a 17d temp offset but at 170 coolant temp, the PCM will "see" 153d temps and might throw a code.

Then you have to figure out which temp sensor controls the fans and the fan turn_on temperature (A/C off). If the fan turn_on is 180d, the actual coolant temperature will be 197d (180 + offset). That being said, this might not be a problem but needs to be thoroughly tested.

Mudbog, I think using a M.C. is a great idea and probably the best solution as it would add the smallest offset required to keep VCM off, but maintain closer temperature accuracy as far as the PCM is concerned.

Just my 2 pennies...
 
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#70 · (Edited)
Sorry, Been busy lately, just getting to the response now after doing some testing.

To summarize my findings:

1. I get the same operating temps as you, around 169-175.

2. VCM kicks in at almost exactly 167 degrees, also as you observed.

3. VCM kicks back out again at a much lower temperature, around 160 to 162 degrees.

4. Running the heater full blast creates a temporary drop of around 2-4 degrees F, but it recovers full operating temperature after a very short while. This is why you never see VCM cutting out when doing this, it doesn't drop enough to cut out VCM. It may delay it's onset if you run it full blast before you get to operating temp, but once you're there, it does nothing. Probably why they built in the hysteresis in the drop out temp, to accommodate exactly this scenario.

5. Using a slightly higher resistor value has worked for me in all situations. I never have any issues. VCM is off at all times no matter what I do. I think the MC idea is way to complicated and completely unnecessary. I'm not looking to gouge anyone on here, I'm just trying to help people out. Adding unnecessary components makes no sense to me. Someone explain to me the logic for doing this? All I'm doing is creating an offset that keeps the temp below the VCM kick in temp for all conditions, I see no reason to add an MC to always keep the temperature just below the cutoff. It's a lot of work and money for what benefit?

6. Using an MC to adjust a digital pot so it just keeps the temp below the VCM threshold may be a very bad idea and I'll tell you why. With the way it is now, it's just a pure offset. I can still monitor the temperature, knowing this offset, and know exactly what my engine temperature really is, so I will know when it begins to overheat (VCM will start to kick in, the needle on the dash will go higher and I can also see it on my diagnostic tool). If I set it to always adjust the pot to keep the PCM thinking it's at one particular temperature, I'll never know it's overheating until something bad happens.
 
#76 ·
I think the MC idea is way to complicated and completely unnecessary.
I'm not opposed to the idea of just using the series resistor to offset the temperature. I just want to consider alternatives and make sure the resistor solution is bullet proof under all scenarios.

Do you or anybody else know exactly what ECT1 is used for besides VCM and the temp gauge? I imagine the shop manual describes it but I haven't bought the shop manual yet for the 2012. If somebody has one can they check it out?
 
#71 ·
Can those of you in really hot climates that have a OBD tool tell me what your actual operating temperatures are? I've never seen anything over 175 or 176. Certainly not 180. Some data from people in warm climates would help. I'll know more here when summer comes, but even then we rarely reach 90F outside temperatures.

I've used my simple harness in outside temps ranging from about -4F to 50F with absolutely no issues and very little change in operating temperature.
 
#77 ·
I've looked in the shop manual and can't find any difinitive answer to that question. Even the wiring diagrams don't help. The manual does not tell you much about PCM programming.
 
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