Sorry for the double post, but I think I've stumbled across some interesting stuff.
1. The code on my gauge cluster/head is 61A80 (with an NZ) next to it. According to KickFix's cross reference list, this part number doesn't exist. Hahah!
2. I have no VSS and the VIN states 92 Vitara.
So my guess is this. A previous owner swapped in a gauge head with no VSS (89) and the check engine illuminated. They likely thought this was simply due to the gauge swap, so they removed the CEL bulb.
Unfortunately, it seems I need VSS on this EFI vehicle (despite the car running great now) and I'll have to find a gauge head with this to eliminate the fault.