A scan tool is a very useful tool and must be used when referred to throughout this section. In addition to displaying DTCs, the scan tool is capable of displaying input status and the data values the RFA 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 RFA system not sending a proper command, or the system that received the command is not responding to the command. Using the driver door lock system function as an example, sending a door lock or unlock message to the driver Door Control Module (DCM) to cycle the door lock can determine if the DCM can actually perform the door lock/unlock function. If the DCM are functioning properly and the RFA system is still unable to operate the door locks then the problem is most likely with the RFA system, or an input to the RFA system.

The scan tool can also be used to display input data the RFA system borrows from other systems on the serial data line. This can assist in determining if the RFA system is actually receiving the correct data values. For example, if the DCMs can properly operate the door locks but the RFA system cannot, the problem could be with the input information the RFA system receives from the Body Control Module (BCM). The RFA system uses key in ignition information from the BCM to determine if the key is IN or OUT of the ignition. Refer to Keyless Entry System Description for input information the RFA system uses to perform its functions.