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DIY - 2008-2010 VCM (Variable Cylinder Management) Disable Procedure

103K views 71 replies 30 participants last post by  nunecoco12345 
#1 ·
The purpose of this thread is to provide a detailed DIY procedure on how to disable the Variable Cylinder Management (VCM) system on 2008-2010 Honda Odyssey’s equipped with VCM engines. I will not discuss rationale or methodology used to arrive at the decision to disable the VCM system. Those discussions can be found in the thread labeled “VCM Long Term Reliabilty” on this site.

Perform this procedure with a cool engine and ignition switch OFF.

Photo's 1 and 2, from left to right, are illustrations of the "REAR" cylinder head. Disconnect the indicated (single wire) connector only. If you disconnect either or both of the remaining (two wire) connectors, the engine will only run in "LIMP HOME MODE". Limp home mode means it is running horribly.

Photo 3 is the "FRONT" cylinder head. Disconnect the indicated (single wire) connector only. If you disconnect the (two wire) connector, the engine will only run in "LIMP HOME MODE". Limp home mode means it is running horribly.

Seal both the connector and the connector cavity in the valve to prevent dirt from entering. Electrical tape is sufficient for this task. Secure the connector to the existing harness with a nylon zip tie.

Drive the vehicle at least 10 miles.

The CEL (Check Engine Light) MAY NOT illuminate immediately.

The ECO light may or may not come on during the test drive.

The CEL should come on the next time you start the vehicle if not sooner. Which means you have successfully disabled the VCM. You should never see the ECO light again unless you reverse this procedure.

Install black electrical tape over CEL on the instrument panel. Do not cover the Maintenance Minder lamp directly below it. It looks like a miniature wrench when illuminated.

Purchase a code scanner that is compatible with the Honda OBDII system. I found the Actron CP9575 is compatible.

Scan for codes. The scanner should read:

P3400 code for CYLINDER DEACTIVATION SYSTEM BANK 1 “PENDING”.

After a few drive cycles the same code remained activated and scanner added:
P3400 code for CYLINDER DEACTIVATION SYSTEM BANK 1 “CONFIRMED”.

The following week I scanned for codes and the scanner read in addition to the P3400 verbiage above:
P3497 code for CYLINDER DEACTIVATION SYSTEM BANK 2 “PENDING”.
P3497 code for CYLINDER DEACTIVATION SYSTEM BANK 2 “CONFIRMED”.

These codes are triggering the CEL illumination. It's the price you pay for no VCM.

If you are in a county that requires vehicle emissions testing, you simply plug the connectors back in. Clear the codes with your scanner. Drive cycle 100 miles, pass the test and disconnect again until next time.

Disclaimer: Anyone who disables VCM in a vehicle may or may not experience similar results and/or negative consequences. Anyone who disables the VCM on their vehicle, regardless of model year, accepts full financial responsibility for any negative consequences that may occur to the altered vehicle

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#4 ·
Thank you kgardonia.

This procedure worked on my 2013 odyssey and my experience has been identical to what you describe above including the very delayed appearance of the P3497 code. The only difference I noticed was the location of the connectors on the rear cylinder head. The ones in your photo are all there, but mine doesn't quite look the same. Still there is only one single-wire connector in that area so it's no problem at all.
 
#6 · (Edited)
"***Keep the success stories coming.***"

OK, been away for a while. Please reference my postings #5 and #12 under "VCM Long Term Reliability" in January of 2012.

That thread got completely lost and the good part came here. Good summary kgardonia.

I now have about 8000 miles with VCM disabled by disconnecting the rocker arm oil pressure sensor. No issues other than the check engine light and that is a non-event, really.
I have added an inline switch to the sensor line to reconnect it for visits to the Honda shop without a CEL.
Good that they extended our warranties, bad that we still have to hack our engines to save them.
I only disconnected the rear sensor, that was all that was needed. Can't hurt a thing, VCM is inactive until warmup on every drive cycle anyway.
Stock VCM only engages when the engine is warmed up and all systems are go. The sensor fault is the simplest way to force the whole system to stay inactive. The ECO light is useless and mostly unrelated to VCM, ignore it.

You're welcome.

Cmoswizard 2008 Odyssey Touring.
 
#7 ·
I have figured out how to activate and deactivate VCM from the cabin using a OEM switch in the blank slot between the rear door switch and the VSA/OFF switch. I purchased the required components, assembled and bench tested the system. I will be installing it this week end.
If there is enough interest, I will do DIY instructions.
 
#8 · (Edited)
I'm just starting my research, because I just drove home yesterday in a new-to-me 2005 EX-L. Right away I knew I wanted the ability to turn VCM off. What is the difference between the 05-07 Ody's, and the 08-10's that makes this procedure specific to the newer 3rd gen?


And yes, I'm interested in any DIY switch instructions you're willing to make. I may be able to use all or some of your method when I start on mine.
 
#9 · (Edited)
What is the difference between the 05-07 Ody's, and the 08-10's that makes this procedure specific to the newer 3rd gen?
Nobody seems to know and nobody has been able to figure it out since, well, 2005. See for yourself below. And don't let the thread name fool you, it's all about understanding and disabling VCM:


I may be able to use all or some of your method when I start on mine.
If you can pull it off, you'll have done something that many have tried and failed at. It will be worth all of the effort that you put into it!
 
#11 ·
The cab switch project appears to be a success. I now can enable or disable VCM from the cabin with a switch installed in one of the blank slots on the IP. See attachment.

The ECU did not react adversely to the relay installed in the rear bank OP switch wire and turn on the CEL. Drove it 30 miles with VCM activated and normal ECO lamp operation, then turned it off. CEL came on in about 6 miles and ECO lamp and VCM system ceased operation. I am optimistic that the project will be long term success.
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#13 ·
The cab switch project appears to be a success. I now can enable or disable VCM from the cabin with a switch installed in one of the blank slots on the IP. See attachment.

The ECU did not react adversely to the relay installed in the rear bank OP switch wire and turn on the CEL. Drove it 30 miles with VCM activated and normal ECO lamp operation, then turned it off. CEL came on in about 6 miles and ECO lamp and VCM system ceased operation. I am optimistic that the project will be long term success.
View attachment 52609
Great info! I have a question though. Did you just attach the switch to the rear bank line? What about the front bank? Can vcm be totally disabled by just unplugging one of the lines and not both? Just wondering because the less I need to unplug the better!
 
#12 ·
Fantastic! Great work. You are so lucky to be rid of it. As my Ody gets older the VCM engage/disengage is even more pronounced and irritating. I almost can't stand it anymore. Ugh.

I'm looking forward to reading all of the other success stories that are inspired by your efforts.
 
#14 ·
Taking cmoswizard's cue from post #6, I disconnected the OP sensor on the rear bank only. ECU disables VCM if any part of the system becomes inoperative.
 
#16 ·
Yes. It is actually that simple. I was concerned the ECU would not like the added relay or splices since there is no way I could duplicate the OEM circuit resistance, but it did not flinch.........
 
#17 ·
Perfect! Thanks for all of your effort on this and the others who have contributed. :)

I have one last question... maybe it was covered before, but what does that single wire connector actually do when it is plugged in and in normal operation? I'm just wondering what the motor is losing when it is disconnected (aside from VCM!).
 
#18 ·
@ megatron

The connector plugs into a basic oil pressure (OP) switch in the cylinder head. When engine oil pressure reaches the desired pressure, the contacts in the switch close to create a ground signal the ECU requires to activate the VCM along with other operating parameters the designers implement. Unless ALL design parameters are met, VCM will not activate.

VCM utilizes the engine oil and basic hydraulic control valves to direct the oil to alter the valve train which deactivates cylinders during VCM operation. Unless there is sufficient oil pressure, VCM will not activate.

The engine loses nothing when the OP switch is disconnected. The oil pressure is still there, the contacts in the switch are still closed, the ECU does not see the ground signal, VCM is not activated and the CEL lamp illuminates.

That is VCM 101 as I understand it. My understanding may change tomorrow.............
 
#19 ·
Diy

The good news is I got the switch DIY instructions done with photo illustrations. The bad news is it is a large file and I'm not sure I can post something that large. If you want a copy, send me private message with your email and I will send it out.
 
#20 ·
Update:

The VCM on/off cab switch is working as intended. After running 3 weeks with VCM disabled, I turned it on last week and did not clear the P3400 code. The ECU turned off the CEL off after 50 miles and VCM and ECO resumed normal operation.

The engine has not consumed any oil since I disabled VCM in May. Roughly 10K miles now.
 
#21 ·
UPDATE:

Engine is running great with better low end torque since spark plug swap. The oil consumption has remained zero and no new MIL codes have materialized. At this point, there are no adverse issues to report. May work on the CEL lamp while the weather is cool.
 
#22 ·
UPDATE:

Nothing new to report. All systems normal. Nothing adverse to report. There is nothing finer than a VCM free engine.
 
#25 ·
I have a 2008 Honda Odyssey Touring. I just disabled VCM, I had to disconnect both single wire harnesses (front and back), disconnecting the back one only did not do the trick. The entire process including the test drive to get a cold engine warm took about 30 minutes. Check engine light came on and eco light was off. This is especially important because I just picked up the van from the dealer after having the 'ring job' work performed under TSB 14-080. It also needed two new valves in the affected cylinder, Honda refused to cover the repair cost of the valves. Anyway, the new rings are in the break in period so it is important that I disable VCM to correctly break in the new rings. I plan on keeping it disabled. Thankfully nothing else goofy has happened, like VSA being disabled. I say this because when I got the check engine for the cylinder misfire (P0301), VSA also became disabled.

Thanks for the great write up. It made this procedure easy enough to finish in an evening after work. Now I can enjoy my Honda Odyssey and hopefully it does not start burning oil again.
 
#26 ·
Keep the reports coming...

Wow, thanks to everyone that worked on this, especially Ken. This should be a sticky to at least let potential owners know about the VCM conversations. I checked this site before I bought my 2010 Ex-L for the sticky information to see if there were any big issues. Placing this as a sticky would bring more awareness to this issue and also this brilliant workaround.

We had the van 3 days and my wife asked me what the engine was doing as she was driving into town on the country road. I did more reading on this site and finally found out what was happening. I unplugged the oil pressure switch and did the electrical tape and zip tie job on it. Now it cruises on all 6 cylinders without sliding into VCM mode. It's strange to have a new (to us) van with the CEL on because it runs on all 6 cylinders. I've been turning wrenches for years and I really though I was getting a nice van with a reliable Honda engine...not having to monkey with it instantly and put electrical tape over a CEL.

Anyway...could someone make this a sticky just as a potential problem and not a guaranteed issue. Thanks to all that have worked on this, more people are coming here and doing this modification than are posting. I've been using forums for years and this is my first post ever! So, thanks again and keep reporting your smooth VCM-free rides. I'm only 1,000 miles in on my VCM-free adventure.

It wasn't awful, but it felt like a low grumble and the engine/transmission were working harder than needed just to cruise up the road and then accelerate a little bit. Seems like an excessive amount of movement for such little documented mpg gain.
 
#29 ·
On the issue of using black electrical tape to cover the CEL light...

I buy a cheap OBD-II scanner (Actron about $45) and keep it in the glovebox, together with a small logbook (small notepad).
Once or twice a month, I scan for "non-VCM" codes and keep a journal such as:
"Jan 29, 2105: no new codes".

Just write down the codes for VCM inside the notepad as reference and ignore them.
 
#30 ·
If I disabled the VCM, the CEL would come on with code P3400.

Would the car fail the state-mandated emission test with VCM disabled permanently ?
 
#31 · (Edited)
It would fail with ANY Check Engine Light on. The key is to re-enable the VCM for a little while BEFORE going for an emission test and then disabling it again afterward. Or do what kgardonia did in another thread and install a switch that actually cuts the connection to that sensor on demand so that you can turn VCM on and off as needed with a button.
 
#32 ·
I'm at 98k miles about to take a long road trip and considering disabling VCM. I burn about 1/2 quart over a 5-6k mile OCI which is unremarkable. New plugs at 97k which looked unremarkable.

For drivability reasons and to avoid being one of the unfortunate folks who get plug fouling and possible subsequent engine damage I want to disable VCM.

Several questions:

1) Does unplugging only one sensor work?

2) I have to pass an annual inspection. If I plug it back in will the CEL clear on its own?

3) If you have to clear the CEL via a code reader how long until the vehicle will pass inspection? (I am pretty sure when you clear codes it sets a flag that the inspection station sees and reports as "not ready" I went through this on an F150 that I changed the battery on shortly before an inspection).

4) Any downside to leaving the VCM system in a disabled state for an extended period of time? Can the valves/sensors/solenoids, etc. clog or stick after being off for a year or so?

For those of us that have to pass an annual inspection that includes OBD2 inspection, bringing the system back to life once a year so the codes can clear is an important issue.
 
#33 ·
Andy,

All my experience is with my 2010. That being said here is what I know:

1/2 quart over 5-6k is not considered a oil consumption problem on an engine with 98k on it. I think if you were going to have oil consumption issues they would have started by now.

- Unplugging one sensor works on the 2010 VCM system. If you plug it back in, the ECU should reset within 20-50 miles, UNLESS you have other codes triggering the CEL. You can clear all codes by simply disconnecting the negative battery cable for 5-7 minutes and then reconnect. However a code reader is a must because you need to scan for codes at least monthly so you can address any other codes that may materialize. Why? Because the CEL will be constantly illuminated when VCM is deactivated in this method.

The drawback to disconnecting the battery is resetting all your save radio stations. My 2010 must have a battery back up in radio because it remembers the saved channels with the battery disconnected.

...WARNING... if you don't have the code to reactivate your radio, don't utilize this method. It is an anti theft feature and the radio will not function until the proper code is entered. See your owners manual.

- I think most jurisdictions want to see 100 mile interval between code clearing and the test. So reactivate a week or so prior to test.

- Your last question is an unknown. I have thought about that and it is the reason I installed the switch in dash so I can run the VCM system about once a month for 50 or so miles just to keep everything "limber" by pushing a button. I believe using a synthetic motor oil and regular on time oil changes should negate those issues. Mine has been disabled since May 2014 with no problems when I re-activate it.

Hope this helps. Good luck.
 
#34 · (Edited)
Thanks for the info.

I agree the oil consumption is not high for my particular vehicle. It has been consistent since new at 1/2 qt for the OCI.

The reason I want to disable VCM is we really don't know the how, why, or what event precipitates VCM motors bypassing enough oil to foul plugs and the subsequent cascading failures that lead to an engine rebuild. There are a few people popping up in the other thread with higher miles so I'm not sure anyone is immune regardless of mileage.

We would like to keep our car as long as possible without making friends with the Honda dealer. Additionally, the settlement doesn't help you after 100k and 10 years (coming up in 2016 for my van). The terms of the settlement are you have no other recourse unless you opted out (whether you knew it or not). Basically I don't want to be driving a van that needs a rebuild at 120k. Then, you would have to pay out of pocket to fix and sell the car at a tremendous loss.

Without VCM enabled I say you have a very limited chance of needing to worry about rebuilding the engine during ownership. With it enabled, who knows?

I may just try it out disabled on my long trip just for the heck of it.

I think your switch solution is a good idea. I would have to find a different place for the switch as I already have something in that spot.

I have a code reader and would dedicate a $20 model to check for CEL codes other than the VCM ones. I can't really say I would do it monthly but often enough.

Does your van immediately put VCM in action when you press the button even though the CEL has not cleared yet?

BTW, where did you run the wiring to enter the cabin?

Has anyone tried plugging in a dummy sensor in the harness? IE the sensor would function and complete the circuit but it would never see pressure as the sensor would be in mid air zip tied off. I wonder if that would cause a CEL or just make the VCM logic fault to a "no activation" state?

Thanks for the help.
 
#35 ·
I have a 2007 EX-L and would like to try the procedure to disable the VCM, but I have not see any definitive postings as to whether this will work on the 2007. Has anyone successfully disabled the VCM on a 2007 EX-L? Is it the same procedure posted by Ken?

By the way Ken, thank you very much for all of your hard work to figure out how to turn off the VCM! I just hope I can get it to work on my 2007.

Now, if there was only a good way to get the CEL to stay off.
 
#37 ·
Andy,

I think it activates but not sure. The ECO lamp doesn't start working again until CEL deactivates.

I ran the wiring through the rubber boot for the water valve on the heater core. Sealed it with silicone.

OEM oil pressure sensors are a single wire switch that completes a ground circuit. If the ECU does not see the ground signal from both OP sensors (one on each bank) it will disable the VCM and activate the CEL.

Ken
 
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