Chevrolet Repair Questions? Ask a Chevy Mechanic for Answers ASAP
The reason why I ask, is because anytime there are MULTIPLE transmission solenoid codes, its usually the result of a failed ignition switch. However, since only two codes appeared and were one at a time, I think at this point, its unlikely the result of an ignition switch failure.
P0785 is for the 3-2 downshift solenoid. Either the solenoid is faulty, or something got damaged while the 1-2 solenoid was being replaced. (connector knocked loose, wire rubbing on pan or valvebody, etc...).
The 3-2 solenoid is #394 in the picture below, which is at the opposite end of the 1-2 solenoid.
Its the key ignition switch, but you don't have enough codes to support replacement of that.