Where can I find the error codes for a Bryant 90 plus

The installation manual and they should be on the inside of the cover on the unit.

We actually had it covered before but for some unexplainable reason the post does not turn up for me quickly, so I'll just type from the Bryant ref. sheet I have in front of me:

11 - NO PREVIOUS CODE 12 - BLOWER ON AFTER POWER UP - normal operation 13 - LIMIT CIRCUIT LOCKOUT 14 - IGNITION LOCKOUT 21 - GAS HEATING LOCKOUT 22 - ABNORMAL FLAME-PROVING SIGNAL 23 - PRESSURE SWITCH DID NOT OPEN 24 - SECONDARY VOLTAGE FUSE IS OPEN 31 - HIGH-HEAT PRESSURE SWITCH OR RELAY DID NOT CLOSE OR REOPENED 32 - LOW-HEAT PRESSURE SWITCH DID NOT CLOSE OR REOPENED 33 - LIMIT CIRCUIT FAULT 34 - IGNITION PROVING FAILURE 43 - LOW-HEAT PRESSURE SWITCH OPEN WHILE HIGHT-HEAT PRESSURE SWITCH IS CLOSED 45 - CONTROL CIRCUITRY LOCKOUT

Hope this helps.