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What is the $ symbol on my OBD2 Device?

By R&D
Published on December 19th, 2023

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The $ symbol is used by programmers when describing different OBD modes which has nothing to do with actual money. 

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For example, mode $06 is an advanced diagnostic functionality mode included as part of the On-Board Diagnostic standard. It keeps track of how emission control components and other systems and sensors are functioning. There are 10 main OBD modes, and they are all represented with a $ in front. This is from mode $01 all the way to mode $10.

In the context of on-board diagnostic (OBD) systems, the $ sign typically represents the special character used to indicate the start of a diagnostic trouble code (DTC) when communicating with the vehicle's OBD system.

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OBD systems are designed to monitor and detect faults in various vehicle systems, such as the engine, transmission, emissions, and other components. When a problem is detected, the OBD system generates a unique code, known as a diagnostic trouble code, to identify the specific issue.

Diagnostic trouble codes are standardized and consist of a combination of letters and numbers. They typically start with a letter, followed by four or five digits. For example, a common format for DTCs is PXXXX, where P indicates that the code is related to the powertrain (engine and transmission).

When retrieving DTCs from an OBD system using a scan tool or diagnostic tool, the $ sign may be used to initiate the communication and request the codes. For instance, to request diagnostic trouble codes from the OBD system, a user might send the command $DTC to the vehicle's onboard computer.

It's important to note that the specific communication protocols and commands used to interact with OBD systems may vary depending on the vehicle's make, model, and model year, as different generations of OBD systems (e.g., OBD-I, OBD-II) have been used in vehicles over the years. Additionally, the $ sign might not be used in all OBD systems, but it's a common convention in many cases.

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