How do you retrieve codes on a 91 park avenue?

To retrieve diagnostic trouble codes (DTCs) on a 1991 Park Avenue, you can use an OBD-I diagnostic tool or a paperclip to short the diagnostic connector. The connector is usually located near the driver's side, under the dash. By bridging the appropriate terminals (often A and B), the check engine light will flash, indicating the codes. Count the flashes to determine the specific trouble codes based on the service manual.