In Unified Diagnostic Services (UDS), RID stands for RoutineIdentifier.
Understanding RoutineIdentifier (RID) in UDS
As stated in diagnostic documentation, RoutineIdentifier (RID) is a crucial part of the Unified Diagnostic Services (UDS) protocol, which is used in automotive diagnostics systems. Its primary function is fundamental to how diagnostic tools interact with Electronic Control Units (ECUs) within a vehicle.
What Does RID Do?
The main purpose of the RID is clear: It helps to identify and execute diagnostic routines on ECUs or Electronic Control Units. Think of it as a unique code or address that points to a specific task or function the ECU is capable of performing for diagnostic or service purposes.
Diagnostic routines can vary widely and include tasks such as:
- Self-tests: Initiating built-in diagnostic checks within the ECU.
- Component activation: Turning specific actuators (like relays, lights, or motors) on or off for testing.
- Calibration procedures: Starting processes to recalibrate sensors or system parameters.
- Specific data acquisition: Triggering the ECU to collect and report particular types of data beyond standard diagnostic trouble codes (DTCs).
- System resets: Performing soft or hard resets of certain ECU functionalities.
How RID is Used
When a diagnostic tool (like a scan tool or specialized software) needs the ECU to perform a specific routine, it sends a UDS request message containing the TesterPresent service (0x3E - although this is often used for keep-alive, the relevant service for routine control is typically RoutineControl 0x31), specifying the desired action (e.g., StartRoutine, StopRoutine, RequestRoutineResults) and the relevant RoutineIdentifier (RID).
The ECU, upon receiving the request, looks up the provided RID in its internal list of supported routines. If the RID is recognized and the requested action is valid for that routine, the ECU executes the task and responds to the diagnostic tool with a confirmation or results.
Key Aspects of RID
| Aspect | Description |
|---|---|
| Identification | Uniquely identifies a specific diagnostic routine within an ECU. |
| Execution | Used in conjunction with UDS services (like RoutineControl 0x31) to start, stop, or query routines. |
| Standardization | While the use of RID is standardized in UDS, the specific RID values (e.g., 0xF001, 0x0200) are defined by the vehicle manufacturer for each ECU. |
| Purpose | Facilitates structured interaction for performing specific diagnostic or service functions. |
Practical Example
Imagine a diagnostic tool needs to perform a test where the Anti-lock Braking System (ABS) pump motor is briefly activated to check its functionality.
- The diagnostic tool sends a UDS
RoutineControl(0x31) request. - This request includes the
StartRoutinesub-function. - Crucially, it includes a specific RoutineIdentifier (RID), let's say
0x0201, which is defined by the manufacturer to correspond to the "ABS Pump Motor Test" routine. - The ABS ECU receives the request, recognizes the RID
0x0201, starts the pump motor test routine, and sends a positive response to the tool.
Without the unique RID, the diagnostic tool wouldn't know which specific routine to ask the ECU to perform.
In summary, the RoutineIdentifier (RID) is the designated label or code within the UDS protocol that allows a diagnostic tool to precisely target and command an ECU to perform a defined diagnostic or service procedure.
