As you noticed the 4cyl doesn't have an AIR pump.
I'm sorry I can't tell you more about the codes without a book. There are at least 40 pages of different codes for engine management systems. Not just different codes but different charts for different models and this is just in the 1993 code book.
I doubt that the codes for a KE-Jetronic would bear any resemblance to those of a HFM-SFI car that Jim has.
Bosch Master, ASE Master, L1
33 years MB technician