I'm on my 2nd Honda Pilot (2004), and I'm trying to figure out why my check engine light is coming on when I activate vtm-4 lock? I've had it read and basically it's saying I need a tune up, but I'm trying to understand the association, because it only comes on when I activate 4 Lock.
Anybody know the connection?

 

Well, first, this post is in the wrong part of the forum. This is the forum help page, for technical issues.

Second, when you lock your differentials (which is what it sounds like you're doing), the loading on the engine changes. There are many issues that only appear when the engine is under load.

If you take it to a mechanic, they can drive it around with a scan tool hooked up, and tell you what happens when you hit the vtm-4 lock, but you might have to ask them to do that specifically.

Sometimes the computer stores the operating conditions present at the time of the error code being set, so you can get that out off the car's memory, and compare it to normal driving at other times.

Good luck!