As previously stated, CV21 lets you bring F1-F8 from consist members to the consist address. CV22 allows you to bring F0, F9-F12. The consist address cannot run more than 13 functions (NMRA standard). Additional functions must still be run at the locomotive original address. These MTH locomotives have 28 functions, but only 16 are available to me on the MS2 anyway. As previously stated functions can be re-mapped to F0-F15 as needed. All of the useful functions can be access in 16 functions, and honestly really in 13 functions.

What is set on CV21 and CV22 mostly depend on the specific locomotive. Some of the items (same sound mute, 128) seem to be universal, but many are not. For this the MTH manual is required.

In the MTH manual there are two pages to look at; page 20 "Function chart" and page 28 "Function identification chart". The former says what feature is assigned to each F key by default. The latter provides the function identification number for these functions. The function identification is what you need to actually set into CV21 and CV22.

For Example, F1 (bell) has a value of 1 and F3 (Startup/Shutdown) has a value of 24 (as seen on page 28 function identification chart). To just make these two available at the consist address, you add them up and set them to CV21 via PoM. So, in this case you would set CV21 via PoM to 25 (24+1).

There is a chart of page 32 that shows values for CV22. CV22 controls whether the headlight is included in the consist, so it's important IMHO. MTH have two lighting features on these locos, F5 controls the running lights and number boards, F0 the headlight/Mars Light. The caveat is that F0 will not really control the headlight unless F5 is activated. So to backtrack, one may want to add teh running lights F5, value 32, to CV21 (24+32+1) = 57. CV22 can be set via PoM to 1 to include the headlight.

CV21 and 22 need to be set on each address that makes up the consist, e.g. DCC 3 and DCC 4 in this case (again, via PoM).

What's interesting to note is that you can assign different functions to different units in the consist. Say you just want DCC 3 to handle the horn and other functions, set CV21 to 57. You want DCC4 not to do the horn, take it out (-1), CV21 to 56. This can also be leveraged if locomotives have different features. In the case of these locos, all four are identical in features other than the fact that the B units have no lighting.

I found that if I set CV 21 and 22 values to 255, all features F0-F12 would be available in the consist. Since the locomotives all have the same features, that works for me, I don't need to exclude one unit from participating in the horns, etc.