Honda Pilot - Honda Pilot Forums banner

VCM disable - a new and better way

583285 Views 1481 Replies 384 Participants Last post by  verbatim
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.

See less See more
  • Like
Reactions: 5
1 - 12 of 1482 Posts
With the A/C off, do the cooling fans come on correctly?
If ECT1 is used for fueling, it may want to go into closed loop right away. Here in Fl this probably isn't a problem.
Is the pot inline with the sensor or is the sensor disconnected and the pot is installed across the sensor leads in the plug?
The pot is inline with the sensor. ECT sensors are thermistors, which means just a resistor that varies with temperature. As the coolant temperature increases, the resistance across it decreases. By adding in more resistance inline with the sensor, you're increasing the resistance of the circuit, which makes the PCM think the engine is cooler than it really is.

The resistance I'm using by adjusting the pot is about 40 ohms, but I may have to adjust it once the weather warms up and the engine runs hotter, I'm not sure.

As mentioned, I still need to confirm that fan operation is unaffected, but so far there have been zero issues with doing this other than the initial code I mentioned that has cleared. I'll also be checking my plugs regularly to look for signs of running rich, but I really highly doubt I'll see anything. If anything, my rear bank plugs will look way better than others have reported.
Fwiw, ECT1 does control the fans. While testing different resistance loads, I was able to get both fans to come on because the temp was reading 230.

So, I believe both ECT's control the fans The ECT by the thermostat will turn the fans on if the thermostat gets stuck closed and the engine gets hot. The other ECT turns the fans on when the leaving water temp from the radiator is to high.

It looks like you are basically offsetting the ECT reading by 2 - 10d? This would still allow ECT1 to turn on the fans if an over temp condition occurred (but offset of the actual temperature).

I think your resistance value will have to be determined by the fan turn on temp (A/C off). Otherwise ECT1 could go higher than 168 and allow VCM operation. This might be 20d or more.
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:
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...
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.
Like I said, I have seen 182d and upper 170's regularly here in Florida.
ECT1 does operate the fans to some degree as I set the temperature to 230d using a resistor and the fans came on high speed (engine was cold).
What is the temperature offset using a 68 ohm resistor?
Just passing along my update on the VCMuzzler. Install was straight forward. Once installed the ride was great. Especially in cruise mode, except for this morning. On my way into work about 5 min. into the drive the CEL came on and said "Check Emission System". That caught me off guard cause I've been using the VCMuzzler for the last month and no issues. Now this morning we had abnormally low temps than the last few weeks. It was 35 degrees so this would have been the first time it would have run in those temps. So I unistalled the VCMuzzler and took it to Advance Auto to have it diagnosed. And sure enough it was the coolant temp out of range "too cold". So with that being said has anybody run into this scenario. I've ordered a OBDII tool to clear the code and will be installing the VCMuzzler. Hopefully it was just a fluke and everything will work out fine in the future. If it does happen again maybe an adjustment needs made to the resistor value. I know that the climate changes and there are many variables. Otherwise the VCMuzzler worked great and my gas mileage was not affected during the time it's been installed.
I stated very early in this discussion, that this might be a problem. To get it to work in warmer climates, you have to have a bigger temperature offset. With the bigger offset, those in colder climates might trigger a CEL due to temperature plausibility (low temperature).
Offset to small, VCM becomes active as one member has stated.

While I think this is a great idea, it won't work 100% all the time for some people.
I don't have an ODB reader what would you guys recommend that's cheap and does the job..
I've used this unit for years on many different vehicles: UltraGauge OBDII Scan tool & Information Center

For the trucks in warmer climates, once you turn the A/C on, odds are the ECO/VCM won't come on. This is due to the cooling fans being on for the A/C. With the A/C on, the fans are also controlled by the high pressure side of the A/C. Basically, they run all of the time.

When the A/C is off, the cooling fans come on at a higher temperature causing the engine to run warmer possibly causing the ECO/VCM to activate.
A few manufacturers already have tamper checksum's built into the PCM code. Some of these can be reset.

I can understand the manufactures not allowing PCM changes especially in diesels. The big three have paid big $$ on warranty replacement engines/parts due to tuners getting enormous amounts of HP/TQ out of these engines. They blow them up, pull the tune out and say "I'm not sure why it blew up".
I personally know of 4 engines repaired or replaced due to this.

Personally, I'm ok with with a "no tamper" (PCM code only) situation while the vehicle is under factory warranty. After that, it's my truck and I'll do whatever I want with it.
I swapped resistors from your harness Verbatim. It works perfectly. What I was saying was that the indicated temp with the 100 ohm resistor while the car was moving at almost any speed (air flowing through the radiator), the indicated temp was always at 158f-160f, never allowing vcm. The only time the temp climbed was while the engine is running and the car not moving. I assume this to be normal, harness mod or not. If the engine is running with no air flowing through the radiator, the temp will always climb until the pcm commands the fans to come on. I'll remove the harness and report back the "real" temp the fans come on at idle. Just curiuos. Are you saying your temps with harness never allow vcm temps even at idle with no air flow through radiator? Again thanks for a great product. What a difference its made!
Do you have your A/C on? If not, that's normal operation. As stated earlier in the thread, I have seen 184°.

Just to reiterate to everyone, if you're driving with the A/C on, your temperature will stay consistent as the fans will run at varying speeds to keep the A/C head pressure down. VCM may never turn on.

With A/C off, the fans are driven by engine temperature only and will cycle on/off causing a larger temperature swing. VCM can randomly turn on.
1 - 12 of 1482 Posts