The On-Demand Self Test option is used to verify that no electrical concerns exist with the air bag Supplemental Restraint System (SRS) . Upon entering the self test, the air bag Electronic Crash Sensor (ECS) module will make an electrical check of each electrical component in the system. If a concern is detected, a DTC is displayed on the scan tool with a brief description of the DTC. Concerns detected during the self test are not stored in memory, unless the same concern was also detected during normal vehicle operation. The self test should always be run after any repair to verify that the repair was successful.