I recently saw a question to Graham Smith regarding a Foton Tunland with the SVS light on and thought I might be able to provide the reader with an answer. This light is for an emission control problem, which is usually caused while the air-conditioning is on, but not necessarily working. Quite a few Tunlands have come in with the air-conditioning compressor relay missing, which then causes this light to come on. If you look in the fuse box in the engine bay (near the fuel filter) you should find the relays in question. To see if this is the actual fault swap the horn relay into the air-conditioning clutch relay spot and it the light should turn off.
Thanks for the tip. It's certainly something worth checking and might provide a simple fix for the owner in question.