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Discussion Starter #1
Does anyone know if there's a way to read diagnostic data from the VCM system? I've had a lot of trouble with sloppy/rough shifts, shuddering and sometimes a feeling of disconnect between the throttle and the drivetrain. It's intermittent, but it seems like most of the symptoms happen once the vehicle is very well warmed up and VCM is fully engaged. I suspect one of the active motor mounts may be defective from the factory and I'm wondering if I can read any diagnostic data from it with a code scanner. I have a rather old OBD-II scanner and it will allow me to check codes and reset them, but would consider something higher end if it could help in diagnosing this issue. And before you tell me to take it into the dealer, I'd rather have all my ducks in a row before I do so -- their apathy level is unparalleled.
 

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With a smart phone and a OBD dongle and free app Torque you can scan, read and clear all codes that the OBD port has available. On top of that with the upgraded, paid version you can turn your phone into a full on display that again can show everything the mfg has available via OBDII
 

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Discussion Starter #3
Thanks Donn. What I'm wondering is if the VCM system can be probed by an off-the-shelf OBD reader, as opposed to a Honda-specific diagnostic tool.
 

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I picked up this tool https://www.obdlink.com/mxbt/ but haven't used it yet on the MDX. With the FORScan app I can access module data on just about every system in my Ford. I don't know that I will have time today but will try out on the MDX this weekend.
 

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So I played around with the OBDLink MX and didn't see any PID's specific for VCM operation. Then I did some internet searching and insofar as I can tell, this is somewhat elusive data. Seems like folks have had success with ScanGauge II and programming it to display VCM on/off. I gather SGII polls 6-7 different outputs and then uses logic to display on/off status.
 

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why not just let the dealer solve the issue rather than voiding a warranty on a new car?

Did you see this post:

I stumbled on what I think is how to reset your transmission on the MDX and possibly other push button Honda vehicles.

To clean the throttle body you have to put the car in accessory mode (press the start button without stepping on the brake) twice.

I then had my daughter step on the gas pedal full down while I cleaned the throttle body. I heard some noise and asked her what happened inside - She told me that the orange engine light went out. I didn’t think anything of it and thought it was just some timeout.

After cleaning I took it for a test drive and the one thing I noticed was the car transmission was as smooth as the first day I bought it home. I mean it was so noticeably smoother I didn’t feel a single shift.

I then went to YouTube university and this is a thing. Put in accessory mode and press and hold the gas full down for at least 30 seconds until the engine light goes out - you may hear a noise (which I did) At least according to what’s out there and what I just experience it worked for my 2015 MDX

Do at your own risk but it seemed to work for me.
 

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you can buy a little VCM defeat device from ebay/amazon for a few dollars to disable it to see if it helps your situation. Lots of accord folks did that when VCM was new and they didn't like the switching to less cylinders. Honda Diagnostic system might be able to test VCM and turn it off but I doubt you'd want to spend the $$$ on it since the real deal is at least 1K.
 
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