View plansVehicle diagnostics,
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57 concise definitions across codes, evidence, signals, modules, networks, hardware, electrification, security, and diagnostic operations.
Covered subjectsCodesDiagnosticsElectricalElectrificationEmissionsEvidenceHardwareIdentityModulesNetworksOBD modesOperationsSecuritySignals
A
- ABSModules
- Anti-lock braking system. Its controller can manage wheel-speed sensing, hydraulic modulation, stability functions, and related faults. Generic emissions OBD-II does not guarantee ABS access.
- Actuator testOperations
- A bidirectional command that asks a controller to operate a component or output for diagnosis. It requires exact support, safe preconditions, and authorization.
- Air-fuel ratio sensorSignals
- A wide-range exhaust sensor used for mixture feedback. Its current or interpreted lambda behavior is not read like a traditional narrowband oxygen-sensor voltage.
B
- BCMModules
- Body control module. It commonly coordinates lighting, access, power modes, security, and other body functions; exact responsibilities vary by vehicle.
- Bidirectional controlOperations
- Diagnostic communication that sends a command to a vehicle controller, rather than only reading data. Examples include actuator tests and some relearns.
C
- CANNetworks
- Controller Area Network, a common vehicle data bus. A vehicle can contain several CAN networks with different speeds, gateways, and access rules.
- CAN FDNetworks
- CAN with Flexible Data Rate, which can carry larger payloads and a faster data phase than classical CAN. It requires compatible interface hardware and software.
- Closed loopSignals
- An operating state in which a controller uses feedback—such as exhaust sensing—to correct a commanded output. Not every condition or powertrain uses the same strategy.
- CodingOperations
- Changing controller configuration or option data. Coding is different from reading, actuator control, adaptation, and flash programming.
- Commanded versus actualDiagnostics
- A comparison between what a controller requested and what a sensor or state reports. The gap is useful only when signal identity, timing, units, and conditions are valid.
- Confirmed codeCodes
- A diagnostic trouble code that met the controller’s confirmation criteria. It is commonly called stored, confirmed, or current depending on the tool and module.
D
- DC-DC converterElectrification
- A device that converts high-voltage battery power to the vehicle’s lower-voltage electrical system in many hybrids and EVs.
- DoIPNetworks
- Diagnostics over Internet Protocol, usually carried over automotive Ethernet. Physical connector presence does not guarantee an interface or application supports it.
- DPFEmissions
- Diesel particulate filter. Its soot, ash, pressure, temperature, and regeneration data require exact definitions and safe service procedures.
- DTCCodes
- Diagnostic trouble code. It records that a controller detected a condition meeting defined criteria; it usually does not name the root-cause part.
E
- ECUModules
- Electronic control unit, used broadly for a vehicle controller. Engine controller is one ECU; modern vehicles contain many.
- EGREmissions
- Exhaust gas recirculation. The system routes controlled exhaust into the intake to manage combustion and emissions.
- ELM327Hardware
- A command interface originally associated with ELM Electronics that translates text commands into several vehicle protocols. Many clones vary substantially in implementation and reliability.
- Enhanced diagnosticsDiagnostics
- Vehicle- or manufacturer-specific access beyond the universal regulated emissions layer, such as non-emissions modules, additional parameters, and exact definitions.
- EVAPEmissions
- Evaporative-emissions control, which contains and monitors fuel vapor using the tank, canister, valves, sensors, and connecting plumbing.
F
- Flash programmingOperations
- Writing controller software or calibration memory. It needs exact files, interface support, stable power, authorization, preflight, and recovery planning.
- Freeze frameEvidence
- A snapshot of selected operating values captured when a qualifying diagnostic fault set. Availability and code association vary.
- Fuel trimSignals
- The controller’s correction to its base fueling command. Positive generally adds fuel and negative generally removes it, but interpretation depends on condition and strategy.
G
- GatewayNetworks
- A controller that routes or filters communication between vehicle networks. A secure gateway can require authenticated authority for protected operations.
- Generic OBD-IIDiagnostics
- The standardized regulated emissions diagnostic layer available on applicable vehicles. It does not mean every controller or service function is universal.
H
- HVAC moduleModules
- The controller for heating, ventilation, and air conditioning functions. Access and data are typically manufacturer-specific.
I
- ImmobilizerSecurity
- A theft-deterrent system that authorizes engine start or vehicle operation. Key and immobilizer service requires strict ownership, credential, and procedure controls.
J
- J2534Hardware
- A pass-through interface standard used for vehicle communication and reprogramming workflows. Capability still depends on the device, driver, OEM software, subscription, cable, and vehicle.
K
- K-lineNetworks
- A single-wire diagnostic communication line used on many older vehicles and controllers, including ISO 9141 and ISO 14230 applications.
L
- LambdaSignals
- A normalized air-fuel measure where 1 represents the stoichiometric target for the fuel in use. Signal meaning depends on the sensor and controller data definition.
- LTFTSignals
- Long-term fuel trim, the learned fueling correction associated with an operating region or strategy.
M
- MAFSignals
- Mass airflow. A MAF sensor estimates the mass of air entering the engine; its value must be interpreted with RPM, load, pressure, temperature, and fuel-control evidence.
- MAPSignals
- Manifold absolute pressure. It reports absolute intake-manifold pressure, not vacuum directly.
- MILCodes
- Malfunction indicator lamp, commonly called the check-engine light. A flashing MIL can indicate a catalyst-damaging active misfire.
- Mode $01OBD modes
- The generic OBD-II service for current powertrain diagnostic data, including supported parameter discovery and many live values.
- Mode $03OBD modes
- The generic OBD-II service that requests stored emissions-related diagnostic trouble codes.
- Mode $06OBD modes
- The generic OBD-II service for onboard monitor test results. Correct identifiers, scaling, units, and limits are essential.
O
- Oxygen sensorSignals
- An exhaust sensor used for oxygen or mixture feedback and catalyst monitoring. Traditional narrowband and wide-range sensors require different interpretation.
P
- PCMModules
- Powertrain control module. Depending on architecture it can combine engine and transmission control or coordinate with a separate TCM.
- Pending codeCodes
- A fault observation that has not necessarily met confirmation criteria. Pending data can expose a developing or intermittent condition.
- Permanent codeCodes
- An emissions code retained until the onboard system completes its own passing verification. A normal clear command should not erase it.
- PIDOBD modes
- Parameter identifier. In generic OBD-II it identifies a requested data item; manufacturer-specific systems use additional identifiers and addressing schemes.
- ProofScanEvidence
- ScanWrench’s evidence record that binds captured diagnostic context to a canonical integrity identifier. It proves record consistency, not that every conclusion is correct or every module was accessed.
R
- Readiness monitorEmissions
- An emissions self-test status showing whether a supported monitor has completed since reset. Supported, complete, and passing are distinct concepts.
- RelearnOperations
- A defined process that teaches or recalibrates a controller after service, component replacement, or state loss. Requirements are application-specific.
S
- SRSModules
- Supplemental restraint system, including airbags, pretensioners, impact sensing, and control logic. It is safety critical and generally requires enhanced access.
- Secure gatewaySecurity
- A network gateway that restricts protected diagnostic functions until an approved authentication and authorization path succeeds.
- SoCElectrification
- State of charge, an estimate of available battery charge relative to the controller’s operating window. It is not the same as battery health.
- SoHElectrification
- State of health, a model or measure of battery condition relative to a reference. Different systems can define and calculate it differently.
- STFTSignals
- Short-term fuel trim, the controller’s relatively fast feedback correction to commanded fueling.
T
- TCMModules
- Transmission control module. Transmission-specific codes and event data often reside here rather than in the generic engine scan.
- TopologyNetworks
- The map of controllers, buses, gateways, and diagnostic paths in a vehicle. Exact topology can change by model, year, option, and market.
- TPMSModules
- Tire-pressure monitoring system. Direct systems use wheel sensors; indirect systems infer pressure changes. Registration and relearn procedures vary.
U
- UDSNetworks
- Unified Diagnostic Services (ISO 14229), a diagnostic protocol framework used across CAN, CAN FD, Ethernet, and other transports.
V
- VINIdentity
- Vehicle identification number. A controller-reported VIN is one identity signal and should be compared with physical and documentary sources.
- VCIHardware
- Vehicle communication interface, the hardware and driver layer between diagnostic software and vehicle networks.
- Voltage dropElectrical
- The voltage measured across a conductor or connection while current flows. It can expose resistance that an unloaded continuity test misses.
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