All DTCs should be cleared from the vehicle and a road test completed before delivery back to a vehicle owner. Some OEMs also use their own descriptors in addition to the SAE standardized formatting. Most modern vehicles also use a 2 character “symptom byte” in addition to the 5-character DTC, to help further define the type of DTC.
DTCs will typically be 5 characters, with the first character denoting the series and characters 2-5 further identifying the system and specific faults. DTCs are grouped in the following categories: P-Series (Powertrain), C-Series (Chassis), B-Series (Body), U-Series (Network). Service Information is required to obtain the proper enable criteria to identify and troubleshoot the root cause. Each DTC has a predefined enable criteria that must be met for the diagnostic routine to run, and the DTC is set when something in the diagnostic routine fails. DTCs are normally retrieved with a compatible scan tool but can also sometimes be accessed through infotainment/instrument cluster procedures.
Process may also include service information research, on-vehicle pin-point testing, and inspecting systems or components in damaged areas.ĭIAGNOSTIC TROUBLE CODE (DTC): Diagnostic Trouble Codes are set when a diagnostic routine fails for a component, system or inter-module communication. Most vehicle platforms after model year 2005 will have all their networked bussed ECUs connected to the J1962 connector to facilitate scan tool connectivity.ĭIAGNOSTICS: The process of determining problems associated with DTCs, scan data or symptoms identified to determine what repairs, calibrations or parts will be necessary for a complete and safe repair. Non-Powertrain systems can be wired to the J1962 connector or the manufacturer can use an alternate connector. Any vehicle which is OBDII-compliant must have its Powertrain system wired to the J1962 connector. Seven of the pin assignments are mandatory by SAE/CARB, and 9 are given manufacturer discretion to wire additional networks outside of the required Legislated OBDII protocols. Always refer to the OEM Service Information for vehicle-specific network wiring schematics.ĭATA LINK CONNECTOR (DLC) aka OBDII CONNECTOR: A standard 16-pin data link connector, known as the SAE J1962 connector, located under the dash on the driver’s side on all model year 1996 and newer vehicles sold in North America. There can also be additional HSCAN, MSCAN and/or SWCAN networks wired to the SAEJ1962 DLC, including pins 1, 3, 9, 11, 12 & 13, depending on the OEM network topology implementation. This network is wired to SAE J1962 Data Link Connector (DLC) pins 6 & 14. As of model year 2008, all vehicles sold in the US are required to implement HSCAN for their Powertrain communications to comply with EPA/CARB regulations. Single Wire CAN (SWCAN) uses a single line for bus communication. High-Speed CAN (HSCAN) and Medium-Speed CAN (MSCAN) use 2-wire, twisted pair bus configurations. CAN has two potential wiring configurations, and multiple baud rate options depending on how the OEM implements the network architecture.
NOTE: Refer to Service manual for Hybrid and electric vehicle procedures on battery support.ĬAN (CONTROLLER AREA NETWORK): CAN is a vehicle communication protocol that has been replacing older legacy protocols on vehicles for diagnostics and module to module communications since model year 2003 in North American vehicles. A battery “jump box” provides a steady voltage level but is generally too low to meet the OEM minimum voltage requirements. Such conditions can prevent the programming event from successfully completing and possibly render the ECU permanently inoperative.
A conventional battery charger can introduce voltage fluctuations and/or may have AC voltage ripple that can affect the communication lines from the vehicle to the application software. Some European manufacturers require voltages over 14.0V DC to successfully complete a programming session. Most manufacturers recommend power supply levels between 13.2-13.8V DC while in a programming session. Due to varying voltage and amperage requirements from the vehicle networks, a conventional battery charger or battery “jump box” are not recommended for any ECU programming events to help eliminate voltage-related programming failures. BATTERY SUPPORT: A suitable battery voltage/programming power supply should be connected to the vehicle battery while the ignition is in Key ON Engine Off (KOEO) mode.