Some Toyota Yaris owners report experiencing alarm malfunctions after a battery drain, which can prevent activation and lead to frustration. Common causes of these issues include a faulty hood switch, dying 12V battery, faulty key fob, door sensors, low key fob battery, internal motion sensors, wiring problems, or a defective body control module. Additionally, a weak or dead battery may trigger false alarms due to inadequate power to the alarm sensors. After a battery drain, owners are advised to troubleshoot by checking the remote battery, inspecting alarm settings, ensuring proper connections, testing sensors, and resetting the alarm system. Addressing the root cause of the battery drain is crucial to restore proper functionality to the alarm system.

Some Toyota Yaris owners report experiencing trunk lock malfunctions that prevent access with the original key and remote release. These issues may stem from a worn or partially seized key cylinder, which can hinder the key's effectiveness. Additionally, a weak or dead remote key fob battery may disrupt signals needed to unlock the trunk. In some cases, owners can utilize the emergency trunk cord located inside the cabin for access. Furthermore, mechanical or electronic faults could also be responsible for the trunk's failure to open, necessitating thorough troubleshooting. If these attempts do not resolve the issue, consulting the owner's manual or contacting a certified Toyota dealer for assistance is advisable. Some owners have noted that if the trunk opens with a copy key but not the original, it may indicate a problem with the original key or the trunk lock mechanism. If common remedies, such as applying WD-40, prove ineffective, seeking professional help may be necessary to address the malfunction.