DIAGNOSTICS: 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. Process may also include service information research, on-vehicle pin-point testing, and inspecting systems or components in damaged areas.
DIAGNOSTIC TROUBLE CODE (DTC): Diagnostic Trouble Codes are set when a diagnostic routine fails for a component, system or inter-module communication. DTCs are normally retrieved with a compatible scan tool but can also sometimes be accessed through infotainment/instrument cluster procedures. 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. Service Information is required to obtain the proper enable criteria to identify and troubleshoot the root cause. DTCs are grouped in the following categories: P-Series (Powertrain), C-Series (Chassis), B-Series (Body), U-Series (Network). DTCs will typically be 5 characters, with the first character denoting the series and characters 2-5 further identifying the system and specific faults. 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. Some OEMs also use their own descriptors in addition to the SAE standardized formatting. All DTCs should be cleared from the vehicle and a road test completed before delivery back to a vehicle owner. Refer to the service information to identify the enable criteria so the road test properly runs the diagnostic routines. Some DTCs may need up to 3 drive cycles to complete the diagnostic routines. DTCs that do not clear normally indicate that additional diagnostic procedures and repairs are needed (see Hard Code). The absence of a Malfunction Indicator Lamp (MIL or dash warning light) is not an indication that no fault codes are present, as many DTCs do not illuminate any lights or warning messages on the instrument cluster. A network scan must be performed using a compatible scan tool to confirm that DTCs are cleared and there are no Pending DTCs.
DIAGNOSTIC TROUBLE CODE DESCRIPTOR: A text explanation of a DTC, which provides the technician or estimator a summary of the fault. Legislated OBDII DTC descriptors are standardized, so all manufacturers use the same terms for the DTC and the summary. Non-Powertrain enhanced DTCs are not standardized and the OEM can use whatever naming structure they deem appropriate.
DRIVE CYCLE: A vehicle road test to successfully run all the OBDII monitor tests. Each manufacturer provides a guide in their service information on criteria to complete a drive cycle for each vehicle model and model year. Most Powertrain DTC routines are run during the first drive cycle but may not illuminate the MIL until the PCM sees successive failures (i.e. more than one drive cycle).
DYNAMIC: driving a vehicle as defined by the OEM to meet specific criteria and conditions
DYNAMIC CALIBRATION: A calibration procedure that requires a vehicle to be put into a learn state and then operated under specified conditions (commonly a road test) in order to complete. The OEM Service information defines the requirements for each vehicle model, model year and system.
DYNAMIC SYSTEMS VERIFICATION (DSV) ROAD TEST: Performed by trained and qualified shop personnel to identify and confirm performance of the vehicle systems (as described above) plus advanced vehicle features and systems including driver assistance and safety systems such as advanced cruise control and safety restraint systems.
FAILURE RECORDS: Enhanced data captures that some OEMs make available to provide additional diagnostic data from the point in time that a DTC is set. (See Freeze Frame Data). Failure Records are an enhancement to the Legislated Freeze Frame dataset.
FAULT: A term to describe something not working on the vehicle as designed. System and circuit faults that are monitored by a module will result in a Diagnostic Trouble Code (DTC) being set. Faults that set
DTCs may or may not produce a symptom; the existence of DTCs may or may not illuminate a warning lamp in the instrument cluster or Driver Information Center.
FLASH: A term to describe a specific type of ECU programming, specifically a write/rewrite of FLASH memory in an ECU. Typically, flash programming will erase and program an entire operating file and may include multiple memory locations within the ECU.
FREEZE FRAME DATA: OBDII Mode $02, which is a requirement for all model year 1996 and newer Powertrain ECUs, where the PCM is required to capture a snapshot of the operating Parameter IDs (PIDs) when the first Powertrain DTC failure occurs. Freeze Frame data can be accessed with any OBDII-compliant scan tool that supports Mode $02. Technicians can utilize this data to help determine the conditions of the initial fault, and to help recreate the fault conditions if the fault is intermittent and not current. The amount of data stored is dependent on the supported PIDs for that vehicle and ECU. Other ECUs, in addition to Powertrain, may also store Freeze Frame data, but it is not an OBDII requirement. (Also see Failure Record).
FUNCTION CHECK: A task to see if a system or component is working as designed and would be part of a Quality Control (QC) check.
GUIDED DIAGNOSTICS: A process that integrates a traditional scan tool with OEM service information to read DTCs from a vehicle, then provide a troubleshooting path for the technician to follow. Used extensively by European manufacturers in their OEM scan tools, the technician is required to perform specific testing procedures and sequences to identify the root cause of the fault(s) reported.
HANDHELD SCAN TOOL: A scan tool that is self-contained as a single device. It could include embedded software, vehicle communication interface, vehicle connection cables and user controls (keypad, touchscreen etc.) Specific handheld scan tool capabilities will vary based on the manufacturer and the brands covered.
HARD FAULT: A DTC that has met enable criteria and is failing some portion of its diagnostic routine. When a hard fault is present, the fault must be located and repaired before the DTC can be cleared or any additional module set up, programming, calibrations etc. can be completed. The OEM Service Information is required to identify the proper troubleshooting routine.
HEALTH CHECK: See SCAN
HISTORY CODE: A DTC that is not currently active. This is a DTC that was set at some previous key cycle or drive cycle, but no longer is failing its diagnostic routine and has passed the modules subsequent self-check. History DTCs may or may not include freeze frame or failure records associated with the code, depending on the type of DTC and the system reporting it.
INITIALIZATION: A software setup procedure for a vehicle system or component, typically performed with a scan tool with appropriate software. Examples could be ADAS radar, windshield/surround cameras, window regulators, brake pedal position, steering angle and HVAC actuators. Initialization is not programming as those two terms are typically used in the automotive repair environment. Initialization needs to be done whenever the OEM service information indicates it is necessary in a repair procedure and is most commonly performed when a component is replaced. If a module or component is replaced, module programming may be necessary prior to initialization.
INSPECT: A stage of the diagnostic process where a technician performs a visual survey of a vehicle, system or component to ascertain if there is any noticeable physical damage.
INTERIM SCAN: A vehicle scan that is performed while a repair is in process, to read/clear any DTCs that may have been set during disassembly/reassembly. Secondarily, it is used to verify if a replaced component needs to be programmed, coded, initialized or calibrated.
INTERMITTENT FAULT: This type of fault occurs when a system or component does not consistently fail its diagnostic routine. Examples could be temperature-related failures, poor electrical connections, and other environmental issues. DTCs may or may not set, depending on the frequency or cause, which makes them generally more difficult to isolate and correct.
J2534-1: An interface standard designed by SAE (Society of Automotive Engineers) and mandated by the US EPA (Environmental Protection Agency) for vehicle Powertrain ECU reprogramming, covering all model year 2004 and forward vehicles sold in North America. Its purpose is to create an API (Application Programming Interface) which would be adopted by all vehicle manufacturers, allowing the Independent Aftermarket (IAM) the ability to reprogram Powertrain ECUs without the need for a special dealer-only tool. J2534-1 has a defined list of communication protocols that must be supported to be fully compliant. Many OEMs added support for non-Powertrain ECUs and expanded coverage for 1996-2003 model years. J2534-1 was used as the communication standard to add support for diagnostics (in addition to ECU programming) and is required for all model year 2018 and forward OEM software applications per the Massachusetts Right-2-Repair legislation signed in 2014.
J2534-2: An extension of J2534-1 and adds additional communication protocols not covered in the original J2534-1 specification. These additional protocols are normally OEM-specific implementations and are submitted by the OEMs to add additional programming and ECU coverage.
KEY CYCLE: The process of changing the ignition state from OFF to RUN and back to OFF or RUN to OFF back to RUN. Key cycles are used by the ECUs to change diagnostic states and power components ON or OFF.
KEY ON ENGINE OFF (KOEO): An ignition mode where the ignition is in the RUN position, but the engine is not running. All electrical accessories would be powered up and operational apart from components used in the operation of the engine (fuel injectors, fuel pump, ignition coils, etc.). Proper care should be exercised in this mode, as the charging system is inoperative, and all powered components will be running off stored battery power. If KOEO mode is used more than a few minutes, a battery maintainer is recommended to prevent discharging the vehicle battery. To confirm you are in the RUN mode, the MIL will be illuminated on the instrument panel. A hybrid vehicle will be in READY mode.
KEY ON ENGINE RUNNING (KOER): An ignition mode where the ignition is in the RUN position and the motor is running. All electrical accessories will be powered up, including fuel injectors, fuel pump, ignition coils, etc., and the charging system will be operational. No external battery maintainer will be required. A hybrid vehicle will be in READY mode, although the engine may not be running based on its charging logic.
LATCHED CODE: A DTC that sets in an ECU that cannot be cleared with a manual process, battery reset or a scan tool, and requires replacement of the module. Common uses for these are Supplemental Restraint System (SRS or airbag) ECUs where the module needs to be replaced after a deployment. This type of DTC is dependent on the manufacturer of the vehicle and the design of the system. A network scan of the vehicle is necessary to determine if a code is latched within a module. OEM service information is required to properly troubleshoot and repair these DTCs.
LIVE DATA: Real-time datasets from an ECU, referred to as Parameter IDs (PIDs), obtained using a scan tool. PIDs can be actual sensor input values, circuit resistance values, sensor outputs, voltages, frequencies, and ECU software and calibration data.
LOG FILES: A series of recorded data by the scan tool which logs activities with an ECU or network. Log files are typically used by technical support personnel and software developers to troubleshoot, bug fix and provide documentation of vehicle communication activities.
MALFUNCTION INDICATOR LAMPS (MIL) aka WARNING LAMPS, WARNING The official OBDII term for the Check Engine Light and is commanded on by the PCM when a Powertrain fault is detected. Every vehicle sold from model year 1988 and forward must be equipped with a MIL, and all vehicles model year 1996 forward are subject to the OBDII regulations governing the criteria to illuminate it. Most vehicles have additional warning lamps, which may include SRS (airbag), stability control/ABS, engine temperature, etc., but these are not regulated or required the way the MIL is. It is common for OBDII compliant vehicles to have DTCs set in various modules and not display any notifications to the driver, and they need to be retrieved with a scan tool to be diagnosed.
OBDII SCAN TOOL: A scan tool that meets the Legislated requirements for Powertrain diagnostics, including the ability to read/clear emissions DTCs, Freeze Frame data, Monitor tests, O2 sensor tests, EVAP performance, catalyst efficiency and misfire detection. All systems beyond the Legislated OBDII specification is considered Enhanced (Proprietary) non-regulated data or advanced scan tool functions. Body controls, Airbags, Anti-lock brakes, Theft Deterrent system, seat belt data, etc. are non-Powertrain and not covered in OBDII, and are implemented by each OEM in a non-standardized methodology.
OEM SCAN TOOL: A scan tool or scan tool application that is designed and used by an OEM for their franchised dealer network. These tools are also available to the Independent Aftermarket for purchase and are sold through an OEM approved channel.
OUTPUT TEST: A bi-directional control from a scan tool to activate a component for diagnostic purposes or operational verification. Examples are controlling components such as headlamps, cooling fans, A/C compressors, wipers, door locks, etc. to verify both the component and the wiring.
PENDING CODE: A DTC type that will not set as current, or active, until it has failed 2 (or 3) consecutive trips. DTCs that are Type B (two-trip) or Type C (three trip) will show as Pending in the PCM when they fail the 1st trip to alert the technician of a fault but will not command the MIL ON. Pending DTCs can only be retrieved with a scan tool.
PERMANENT CODE: A DTC that cannot be cleared with a scan tool. Permanent DTCs were introduced in 2009 by the California Air Resource Board (CARB) as an addition to OBDII and are only associated with emissions DTCs (OBDII). These types of DTCs require the reporting system to rerun the diagnostic routine (with the appropriate enable criteria) to verify that the system has been repaired. A permanent DTC does not mean there is a current fault, only that the system has not passed the internal self-test for that DTC. After a scan tool clear request, if the DTC routine fails the self-test it will move from permanent to current.
PIN-POINT DIAGNOSTICS (ON-VEHICLE TESTING): Procedures necessary to troubleshoot a fault after scan data and/or DTCs are retrieved, and can include visual inspections, circuit testing wiring repairs, and electrical tests with voltmeters or test lamps. Additional diagnostic and electrical testing skills following service information test procedures must be followed.
PRE-SCAN (PRE-REPAIR SCAN, INSPECTION SCAN or HEALTH CHECK): A network health check performed with a scan tool before repairs or disassembly begins. The Pre-scan allows a technician or estimator to develop a diagnostic roadmap, assess non-visible damage and help identify pre-existing conditions. Pre-scanning a vehicle is an essential step in documenting the nature of the repair and developing an approved course of repair.
POST-SCAN (POST REPAIR SCAN, COMPLETION SCAN or HEALTH CHECK): A network health check performed with a scan tool after all repairs have been performed and verified. A Post-scan allows a technician or estimator to confirm all the monitored vehicle systems are operating properly, and there are no pending or current DTCs. Post-scanning is an integral step in the final QC process before the vehicle is returned to the customer.
PROGRAMMING: A procedure that must be performed to any replacement ECU that does not contain correct operating software for the vehicle it is being installed into. Commonly referred to as FLASH Programming, many replacement ECUs contain a service calibration only, which is software that allows it to communicate with a scan tool or J2534 device, but do not have the full install of operating software. The OEM service information will instruct the technician when ECU programming is required, and what tool(s) are necessary to complete the programming process. All model year 2004 and newer Powertrain ECUs can be programmed using the OEM software and a J2534-2 compatible hardware interface. Some non-Powertrain ECUs can only be programmed using the OEM scan tool and software.
RE-LEARN: See “Calibration”
ROAD TEST BASIC: Performed by shop personnel to verify standard vehicle performance and condition, including – but not limited to, centered steering wheel, vibrations, pulling conditions, wind noise, rattles, engine performance, transmission shifting, etc.
SCAN: The process of using a scan tool to query vehicle network busses to identify which ECUs are equipped, communicating and have DTCs stored.
SCAN TOOL: A device used to query vehicle network busses to identify which ECUs are equipped, communicating and have DTCs stored. Capabilities can vary from simple OBDII readers to highly complex tools that can run guided diagnostic routines. OEM scan tools are generally limited to the manufacturer branding support only but have the complete suite of capabilities as determined by the OEM service engineering groups. Scan tools can come in a variety of hardware and software configurations including PC/laptop-based tools connected with a vehicle interface, to handheld (embedded) tools with built in interfaces and software.
SERVICE INFORMATION: Vehicle repair information, schematics, wiring diagrams, calibration procedures, repair and diagnostic test procedures. There are multiple sources for information ranging from OEM specific websites to all-inclusive aftermarket providers who provide service information for multiple OEMs. Subscriptions for service information must be purchased from providers whether OEM or aftermarket. OEM service information subscriptions are available in short term, monthly and annual terms, and are purchased directly on the OEM service websites.
STATIC CALIBRATION: A calibration that is done to a vehicle in a fixed position based on instructions in the OEM service information. Most static calibrations are done with a scan tool, but some can be completed through the vehicle infotainment system or instrument cluster. Static calibrations normally require a target or reference object and are most often associated with camera and radar replacements/repairs.
TEST: A stage of the diagnostic process where a technician performs a predetermined procedure on a vehicle, system or component. Examples could be using bi-directional controls on a scan tool, using a DVOM to check resistance on an electrical circuit, or activating a driver safety feature.
VEHICLE COMMUNICATION INTERFACE (VCI): A hardware interface between a laptop, tablet, or PC to allow application-based scan tool software to communicate with a vehicle. These devices contain the necessary hardware and firmware to connect the application software to the vehicle networks, utilizing pre-defined SAE/ISO communication protocol standards.
VERIFICATION: proving out proper driving & handling characteristics, wind noise, rattles, squeaks and the proper operation of any/all ADAS equipment on the vehicle regardless of whether the shop serviced that system or not.
ZERO-POINT CALIBRATION: A type of static calibration, most commonly used for
occupant detection and steering angle calibrations. It can also apply to brake pedal position sensors and Idle air control “Idle learn” procedures. This type of calibration is done to establish a zero point for the computer (0 lbs. for an occupant detector, 0 degrees for a steering angle sensor, etc.).