Fleet and procurement managers considering telematics devices have to make decisions based on a number of factors. One of these is whether to use a solution that collects vehicle data from the OBD (On-Board Diagnostics) port, or one that reads data from the vehicle CAN network.

On first glance, this may seem an easy decision.

OBD devices plug into a standard vehicle diagnostic connector and request data from the vehicle using the OBD protocol. OBD devices are generally low-cost and appear to provide a simple and standard install option for aftermarket telematics.

But all is not as simple as it seems

As usual, the devil is in the detail – but first, a quick recap on OBD history.

The OBD standard was created as a means to help monitor and manage vehicle emissions. It was designed specifically to support garage diagnostic tools so they could interface with the vehicle’s engine management unit – and other components – whilst the vehicle was under test (for example, on a rolling road). OBD (technically, it’s now the OBD-II standard) has become the de facto diagnostic and service enabler and is extensively used by both franchised dealers and independent service outlets.

Over time, vehicle manufacturers extended the data you can get from OBD. Often in a proprietary way, they sometimes included ‘privileged’ commands such as ‘unlock the vehicle’ and ‘start/stop the engine’. Manufacturers attempted to secure these privileged commands and data by making them hard to interpret, and through proprietary protocol extensions.

Meanwhile, a number of telematics companies identified the OBD port as a way of obtaining vehicle data. They used it to support the delivery of new fleet telematics services and started to exploit it in their solutions. Early versions often included a number of estimated readings, for example, fuel use. This was based on an extrapolation of emission-related parameters available from the OBD (quite inaccurate, but it provided a rough indication) and by retrieving some of the maintenance & diagnostic information.

Many telematics providers still use the OBD as their access route for vehicle data. But if you're considering OBD as a basis for telematics, there are some things to bear in mind.

Plug & Play?

OBD Plug & Play is largely a myth, at least for commercial-grade telematics. Most vehicles require professional installation due to the position of the OBD port. Many BMW models, for example, have the OBD socket located in the door frame, meaning the door cannot be closed if a device is inserted. In these instances, the engineer must identify the socket location and then remove trim and covers to allow a cable to be routed that doesn’t obstruct the door or other parts of the dashboard. The physical orientation and placement of the OBD device also needs to be chosen carefully to achieve good GPS performance.


As the OBD port is typically user-accessible, tampering is much more common on OBD deployments. It isn't difficult for drivers to easily remove the OBD cable or device. Also, when a vehicle is serviced, the technician will have to remove the cable or device in order to connect their tools. If they don’t, their systems can conflict with the OBD device, halting or slowing down the service. If they remove it, they often forget or are unwilling to reconnect the device.

Vehicle integrity and security

The OBD device is intrusive in the sense that the OBD repeatedly sends messages (system ‘calls’) to the vehicle computer to request data. In some circumstances this can lead to unwanted behaviour by the vehicle’s systems. For example, the car alarm could go off, or the warning lights come on.

Moreover, as the OBD device is able to ‘command’ the vehicle, it's a potential safety and security weakness.

As the OBD device is connected via 2G/3G/4G – potentially to the internet – it is theoretically able to be hacked. A successful attack could then interfere with the vehicle, even whilst it is in motion, or unlock it so that it can be stolen. Indeed, there are plenty of online resources aimed at hacking vehicles via the OBD connector.

Vehicle manufacturer support

You might also want to consider that manufacturers still discourage OBD connected devices. Some are actively taking action to make it difficult for the OBD port to be used for anything other than the connection of service and maintenance diagnostics equipment, and there are proposals to close the OBD access path completely when the car is in motion. Moreover, some manufacturers have intimated that they will remove OBD ports on new models.

“OBD has been designed to service cars in repair shops. In no way, it has been intended to allow third parties to build a form of data-driven economy on the access through this interface.” Christoph Grote, SVP Electronics, BMW


And finally, there are potential legal complications. It is possible that under certain circumstances the use of OBD connected devices when the vehicle is in motion may impact how warranty or liability claims are viewed by the vehicle manufacturer.

The case for CAN

The technology behind CAN (Controller Area Network, also referred to as CAN bus) has been around since 1986. It's the accepted universal automotive standard for connecting electronic devices to vehicles.

Given its ubiquity and the fact that almost all critical vehicle functions are managed via the CAN, it's a logical way to monitor and capture accurate and real-time vehicle data.

Some telematics companies acquire vehicle data from the CAN, but a key challenge is to do so in a non-intrusive way. Cutting or soldering connections to the vehicle CAN network can disturb its operation, or worse.

masternaut can clip

Which is why Masternaut invested in an innovative and patented approach to acquiring CAN data.

To retain the integrity of the CAN, Masternaut engineers devised and developed the ‘CAN bus clip’, a non-intrusive reading device that clips to the outside of a cable behind the dashboard.

It doesn’t puncture the protective sheath around the cable, causes no damage and ‘senses’ data directly from the CAN network.

Because the reader doesn’t have direct access to the computer network and doesn’t place any electronic requests on the CAN itself, the vehicle can’t be hacked. The CANbus clip is safe, reliable and coded to understand each make and model on your fleet. And because it’s a non-intrusive technology, it doesn't invalidate your statutory warranty.

Hidden away, it’s protected against theft and tampering, providing exactly the data you need. And it's guaranteed to work effectively.

“Comparing GPS-based estimates to CAN bus information is like comparing a sundial to a stopwatch. You want to have a fact-based conversation with your colleagues about how to improve things, not a conversation about who is right.” Franc Nicoletti, Product Manager, Masternaut.


As in many aspects of life, you need to weigh the pros against the cons. OBD-based systems have some advantages, typically in terms of a reduced installation time and cost. But as we’ve discussed, they tend to be insecure and provide lower performance, so ultimately are a compromise.

Solutions that can connect directly to the CAN in a proven non-intrusive way may well come at a slight premium. But in this case, the old adage proves true: you get what you pay for.

For more information about our CAN clip please click here.

By Alex Rothwell on Jul 29 2018

Senior Executive with successful track record leading and transforming global teams to deliver high performance. 25+ years’ experience in the software and technology sector, creating & delivering SaaS, mobile, and embedded products and services.

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