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GM and several other manufacturers have added additional information to the 5 digit codes. These are not “codes” but are “Symptom categories”. The DTC symptom is made up of an additional 2 digit code that is place after the 5 digit code (usually a space between the two codes) The first digit following the DTC indicates the symptom category, while the second digit refers to the subsystem or a more in depth information about the symptom. There are 16 possible symptom categories available for 0 to 9 and A to F. Currently there are only 8 categories in use, 0 through 7

My question is where can I get a comprehensive list of these symptom categories and subsystems?

Internet is not of much use to me!

I can find Symptom categories 0 to 7 online.

8 to F are reserved for future use. Have these been allocated?

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Outside of paid service information like ProDemand or AllData, I think you'll have very little luck finding this information. Here's a sample from a 2012 Impala. The list is too long to post the whole thing, but you can infer the meaning of some of the symptom codes from it.

U0073 71 ECU HS Bus Off
U0073 72 ECU LS Bus Off
U0100 00 Lost Communication with Engine/Powertrain Control Module (ECM/PCM)
U0100 75 Lost Communication with Engine/Powertrain Control Module (ECM)
U0100 7F Lost Communication with Engine/Powertrain Control Module (ECM)
U0101 00 Lost Communication with Transmission Control Module (TCM)
U0101 75 Lost Communication with Transmission Control Module (TCM)
U0104 00 Lost Communication with Cruise Control Module
U0104 7F Lost Communication with Cruise Control Module
U0151 00 Lost Communication with Inflatable Restraint Sensing and Diagnostic Module (SDM)
U0151 71 Lost Communication with Inflatable Restraint Sensing and Diagnostic Module (SDM) Invalid Serial Data Received
U0151 7F Lost Communication with Restraints Control Inflatable Restraint Sensing and Diagnostic Module (SDM) Erratic
U0401 00 Invalid Data Received From ECM
U0401 72 Invalid Data Received From ECM Message Counter Incorrect
U0401 74 Invalid Data Received From ECM Bus Signal Checksum Error
U0402 72 Invalid Data Received From Transmission Control Module Message Counter Incorrect
U0402 73 Invalid Data Received From Transmission Control Module Parity Error
U0402 74 Invalid Data Received From Transmission Control Module Bus Signal Checksum Error
U0405 71 Invalid Data Received From Cruise Control Module Invalid Data
U0405 72 Invalid Data Received From Cruise Control Module Message Counter Incorrect
U0405 74 Invalid Data Received From Cruise Control Module Bus Signal Checksum Error
U0415 00 Invalid Data Received From Electronic Brake Control Module
U0415 72 Invalid Data Received From Electronic Brake Control Module Message Counter Incorrect
U0415 74 Invalid Data Received From Electronic Brake Control Module Bus Signal Checksum Error
U0416 00 Invalid Data Received From Vehicle Dynamics Control Module
U0416 72 Invalid Data Received From Vehicle Dynamics Control Module Message Counter Incorrect
U0416 74 Invalid Data Received From Vehicle Dynamics Control Module Bus Signal Checksum Error

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2
  • Thanks so much. Am cool with the 5 digit DTCs, apparently I have to subscribe to data sources such as you listed to access the extra 2 digit codes
    – ElectronicsNewbie
    Mar 21, 2017 at 22:29
  • Thanks for adding the info, Ben. Over the top as usual :o)
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Mar 21, 2017 at 22:53

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