Electronic Systems Trouble Codes for Toyota and Lexus Powertrain codes, Body codes. The remaining characters designate the system associated with the fault. The characters are hex and can range from 0 – F. The third digit defines the specific system or sub-system within the car where the problem is located: Third digit / System or sub-system. 1 Fuel and Air Metering 2 Fuel and Air Metering (injector circuit malfunction only) 3 Ignition System or Misfire 4 Auxiliary Emission Control System 5 Vehicle Speed Control and Idle Control System 6 Computer Output Circuits 7 Transmissions 8 Transmissions 9 Control Modules, input and output signals. Testifying on behalf of the Alliance of Automobile Manufacturers, Greg Dana, Vice President for Environmental Affairs stated, “Historically, about 75 percent of vehicle service and repairs are performed in non-dealer shops. Another issue that is related to OBD II is that of reprogramming vehicle computers.