An essential piece of kit for all car and van owners - save time and money with the D900 CanScan universal code reader which enables you to troubleshoot any problems in your vehicle by reading the Diagnostic Trouble Codes (DTC's) that appear when the "check engine" light is showing. DTC's are codes that are stored by the car's in-board computer system in response to a vehicle issue. Codes relate to a particular problem and are used as a guide to help locate the fault in order for you to fix the vehicle.