The OBD2 port in your car is a gateway to a wealth of diagnostic information, accessing the raw CAN bus network that underpins your vehicle’s communication systems. This port allows devices to query various onboard computers and receive data in a standardized OBD2 format. Interestingly, auxiliary CAN bus connectors, like those found behind car radios, tap into the very same CAN bus network as the OBD2 port. In theory, you could even send OBD2 commands through these alternative connectors. Essentially, both the OBD2 port and auxiliary CAN bus connections offer access to the same unfiltered CAN bus traffic within your vehicle’s single network architecture, unlike some vehicles which might employ multiple networks for critical and non-critical systems.
Given this shared access, the question naturally arises: Can you safely and effectively run 2 devices on one OBD2 port? Using a splitter cable to connect two devices to the OBD2 port, or even utilizing an auxiliary CAN bus connector alongside the OBD2 port, might seem like a convenient way to gather more data or run multiple diagnostics simultaneously. While technically feasible, this approach introduces potential complications that are crucial to understand before attempting to connect 2 Devices On Obd2.
In theory, both devices connected to the OBD2 port should operate independently. However, a significant issue can arise when both devices interpret the same data request. Imagine a scenario where device 1 initiates a query for oil temperature. Both device 1 and device 2 might process the returning data, with device 2 incorrectly assuming the information is intended for its own operation. This type of conflict is particularly likely with multi-stage queries, such as those commonly used for oil temperature readings, which involve an initial request followed by a subsequent data retrieval command. The way each device handles these complex queries can lead to unpredictable behavior and potentially render one or both devices ineffective when you use 2 devices on obd2.
Another critical factor to consider is the query rate of each device. If device 1 is set to query data at a rate of 100Hz, and device 2 is also querying at 100Hz, the combined demand on the OBD2 system becomes substantial. This raises concerns about overloading the CAN bus network. Remember, the CAN bus is not solely dedicated to OBD2 communication; other vital vehicle systems, such as the Vehicle Stability Control (VSC) module, also rely on this network for communication. Flooding the CAN bus with excessive queries from 2 devices on obd2 could potentially disrupt the communication of these critical systems, leading to unpredictable and potentially unsafe vehicle operation.
Therefore, while the idea of using 2 devices on obd2 might seem appealing for enhanced data acquisition, it’s generally advisable to proceed with caution. Unless you can definitively guarantee that the second device operates purely passively – meaning it only listens to CAN bus traffic and does not actively send queries – it’s safer to limit yourself to a single active device connected to the OBD2 port.
For users needing advanced data logging or performance monitoring, consider dedicated devices designed for these purposes. For iPhone users, the AIM Solo DL 2 is a robust option with its own dedicated app. Similarly, Racelogic offers excellent solutions with Android app compatibility. Racechrono is another platform capable of receiving car data through specific formats. However, it’s important to note that these professional-grade devices like AIM and Racelogic are typically designed for standalone operation and may not prioritize compatibility with third-party applications like Racechrono for simultaneous data sharing from 2 devices on obd2 connected via splitters.
Originally Posted by Turbo
Please excuse me being a noob about all this, but how does hard wiring the Racepak that way allow the data stream to operate differently from having both connected to the OBD2 port via a Y-connector? I had the idea of using a bluetooth receiver to connect my OBDLink LX OBD2 scanner to the Racepak (since I was pretty sure that scanner is capable of connecting to more then 1 device at a time) but was told by a Racepak user that Racepak doesn’t have any way to do that.
In conclusion, while technically possible to connect 2 devices on obd2 using splitters or auxiliary connections, it is generally not recommended for active devices that send queries. The potential for query conflicts and CAN bus overload outweighs the benefits in most typical user scenarios. Prioritize using a single, reliable OBD2 device or explore passive secondary devices if simultaneous monitoring is required. For advanced users needing to integrate multiple data streams, consider professional-grade solutions designed for data logging and analysis, keeping in mind their intended standalone operation and compatibility limitations when considering 2 devices on obd2 setups.
