Came across this page in my book for my Drivability and Emissions class. I thought this info would be useful for anyone trying to read OBD II codes. OBD II has a million codes. You won't have the entire code list with you at all times and some cheap scanners won't tell you what the codes are. So here is some quick info to help you read the code(s): OBD II diagnostic trouble codes (DTC) have five characters: a letter followed by four numbers. The first character is a letter identifying the area of the vehicle that the code relates to. * P - Powertrain * B - Body * C - Chassis * U - Network communications The second character is a 0 or 1, indicating a SAE/Generic or manufacturer-specific code. * 0 - SAE/Generic * 1 Manufacturer-specific The third character is a number from 1 through 8 representing the affected powertrain subsystem. * 1 - Air-fuel control * 2 - Fuel system and injectors * 3 - Ignition system/misfire * 4 - Auxiliary emission controls (EGR, AIR, CAT, EVAP) (AIR = Air Injection Systems) * 5 - Vehicle speed/idle control and auxiliary inputs * 6 - Computer system (PCM or communications) * 7 - Transaxle/transmission * 8 - Transaxle/transmission The last two characters indicate the actual fault code listing the sensor or circuit where the code has occurred. Example, 03 = cylinder 3. However, I've seen codes end in high numbers like 42. Obviously there is no 42nd cylinder so if anyone can clarify the high numbers, that would be great. My instructor couldn't clarify this either lol. Also, I know 7 and 8 are the same. According to my instructor, it may be because there are so many transmission codes they had to break them up into two sections. If anyone has different info on this, please share.