85: is undefined ratio error
87: is high ratio error
All are trans. related and likely one of the two 20-30$ input/output trans. sensors or as gmctd pointed out a wiring issue.
93 Chev C2500 HD extended cab, long box, 6.5TDF, 4L80E, DB2 injection pump turned up 1/4 turn, flowmaster downpipe, EGT/Boost/Trans. Gauges, 97+ dual thermostates and HO water pump, 97+ round air filter, manual lockup torque conveter switch, homemade wastegate controller set at 8psi, de-snorckeled, 97+ air filter, 3.43 ratio rear gears, autometer gauges, 19 mpg.