No, RAIM is a different kettle of water.
A 'GPS PRIMARY LOST' message simply indicates that the GPS signal from one or both MMR(s) has been lost. You could get this through something as simple as placing a small sheet of steel over the antenna, having a wire come loose, or anything else that restricts the signal from reaching the receiver.
RAIM detects faults with redundant GPS pseudorange measurements. That is, when more satellites are available than needed to produce a position fix, the extra pseudoranges should all be consistent with the computed position.
This is obviously the short story. If you need more details, let me know.
Last edited by PappyJ; 13th May 2013 at 21:01.