This article provides a detailed account of the troubleshooting and diagnosis process of the occasional automatic opening of the trunk lid due to water corrosion of the switch plug of the trunk lid opener in the 21M Accord CV3 model. Through systematic inspection, troubleshooting, maintenance operations and subsequent verification, a complete set of operation procedures is provided for maintenance personnel to ensure that faults can be resolved quickly and accurately, and at the same time prevent similar problems from happening again.