I brought a OBD 1 code reader from autozone and a Haynes manuel for my car. I scanned the car for code and?

came up with code 26. In the Code scanner booklet that use the codes says 26 means quad driver error No.1. But In the Haynes manuel it says code 26 ECM failer. Which One should I go by? The car runs good and stuff so I dont know. I have a 1990 buick riviera