[speedlever]

My VTM-4 light on dash comes on after I start the vehicle and put it in gear. I tried pushing the VTM-4 button on dash and it doesn't do anything, no little LED light nothing. If I turn the truck off and then back on the VTM-4 light is off until I put it in gear, then comes on.
Any ideas on what the cause of this is?

Do you mean this indicator?

If that's it, check your OM for more information. You likely need to get it checked by a competent shop.

 

[speedlever]

I don't think I would have connected the dots to align a VTM-4 light with an O2 sensor. Wow.