WARNING: This page is about a different car, the 1994 Cadillac Fleetwood. However, it is still accessible from the selected car via links, so may be relevant.
An out-of-calibration A/C pressure sensor or A/C evaporator temperature sensor could cause Code 61 to set.
Fig 1: Code 61 Schematic (Fleetwood) A/C System Performance
Fig 2: Code 61 Flow Chart (Fleetwood) A/C System Performance