A scan tool is a very useful tool and must be used when referred to throughout this section. In addition to displaying DTC(s), the scan tool is capable of displaying input status and data values the Remote Keyless Entry (RKE) system uses to perform certain functions. It is also capable of sending specific commands to other systems to determine if the malfunction is due to the RKE system not sending a proper command, or the system that received the command is not responding to the command. Using the door lock test in Special Functions as an example, sending a door lock or unlock message to the Body Control Module (BCM) to cycle the door lock can determine if the BCM can actually perform the door lock/unlock function. If the BCM is functioning properly and the RKE system is still unable to operate the door locks then the problem is most likely with the RKE system, or an input to the RKE system.