Published in · 6 min read · May 5, 2020
With the emergence of the ELD mandate, trucks of all shapes, sizes, and ages have resulted in the need to install electronic logging systems into their cabs. Mandate rules clearly state that compliance requires ELDs to synchronize on data from the truck’s engine control module (ECM) or vehicle data bus for all model years dating back to 2000. Over the past 20 years, a wide range of network communication standards have been used inside trucks, putting the onus on ELD vendors to connect to a wide variety of physical interfaces and communication protocols.
This presents a unique challenge when developing an ELD platform for older heavy trucks. The technologies used on these trucks lack many of the advancements engineers have come to rely on in modern network technology. One of the key differentiating factors of the KeepTruckin ELD platform is its ability to natively support trucks of a wide range of ages through the support of a wide range of interface technologies without any additional hardware.
This article focuses on how KeepTruckin overcame some of these challenges as well as the benefits a fleet manager might see by accessing these older interfaces.
Before we dive in, let’s define what we mean by an “older” truck. For the sake of this article, we are limiting our definition to those heavy trucks relying on the SAE J1708 physical standard for accessing diagnostics.
Similar to an RS-485 serial network, the SAE J1708 standard allowed automotive engineers to directly tie ECUs through the vehicle together using a single twisted wire pair backbone. Although not very fast (9600 bits per second), this network-enabled reliable data transmission by one node to all other nodes simultaneously.
How to identify a truck using this standard? The most common way to identify if a truck is using the SAE J1708 standard is to look at the diagnostic connector inside the truck cab. If a grey 6 pin or 9 pin connector is inside, there is a good chance that this truck is using some form of the SAE J1708 specification.
Beginning in the early 1990s, the automotive industry has slowly, over time, introduced new standard access technologies as the primary form of communicating with the truck’s ECUs and internal data bus. Once a new standard is adopted, these technologies are implemented gradually in planned stages, allowing manufacturers time to adopt slowly and maintain quality.
The SAE J1708 standard was first introduced as a standard heavy vehicle interface with the adoption of the 6 pin Deutsch diagnostic connector back in the early 1990s. Starting in 2001, a new 9 pin Deutsch connector standard started to appear alongside the introduction of the control area network (CAN) specification as a secondary means to access a vehicle’s internal data bus. The key advantage of CAN was that the intelligence of interacting with the network (e.g. arbitration, prioritization, error detection) was pushed inside a dedicated computer chip resulting in increased reliability and higher data throughput.
There are several reasons why it is important to support these older vehicles.
Perhaps the most obvious reason would be to ensure these older vehicles are compliant with the myriad of regulations fleet managers see on a daily basis. As stated earlier, all trucks model year 2000 or later fall under the jurisdiction of the ELD mandate. This requires any fleet owner running a J1708 only vehicle (6 pin diagnostic connector) to have an ELD which supports SAE J1708.
It is important to note that not all compliance rules stop at the year 2000 like the ELD mandate. Fleet managers may want to take advantage of all features and reporting offered from their telematics platform regardless of the vehicle manufacturer date. Some such features include:
- IFTA fuel tax reporting
- Fault code reporting
- Vehicle usage
- Driver performance monitoring
- Maintenance tracking
Heavy trucks are designed to run for a long time with vehicles commonly hitting odometer readings over one million miles. As a result, many fleets have mixed vehicle types spanning a wide range of ages. Having a platform capable of reading telematics data across all model years provides a big advantage to fleet managers by providing a complete view of the fleet under a single platform.
Having access to accurate and complete data is the cornerstone of operating a fleet efficiently. In the automotive world, when new technologies are standardized, adoption is rolled out in planned stages spanning several truck model years. By not having J1708 support, some platforms may be missing ECU data which has yet been moved over to J1939 in these transition years.
Despite the introduction of CAN in new vehicles in model year 2001, the SAE J1708 has stayed heavily in use until it’s rapid decline in vehicle model year 2012. Having the capability to directly access SAE J1708 opens the door to additional ECUs and data, providing a more complete picture of the state of the connected vehicle. Diagnostic trouble codes (DTCs), can be accessed from both networks providing additional insight into the vehicle state. Redundant data fields can be compared against each network to help ensure data quality, leading to robust designs. Finally, having access to additional data parameters to help identify sensor fault while in the field. Curious how additional data parameters can make an ELD more accurate? Check out our article on being Haunted by Phantom Events.
Let’s explore what it takes to support trucks utilizing the SAE J1708 standard.
Before accessing a vehicle’s SAE J1708 network, the KeepTruckin ELD hardware needs to be in place. KeepTruckin offers the required cabling to directly connect to the grey SAE 6 pin and 9 pin diagnostic interfaces in older trucks. Once the proper connections are made, the onboard SAE J1708 transceiver inside each ELD provides the proper electrical translation to start accessing data.
Unlike new CAN-based networks, which rely on dedicated chips to handle network interaction, interfacing with an SAE J1708 network requires custom software that has precise timing and direct hardware control to be successful.
A successful driver requires constant monitoring of the SAE J1708 bus state. The standard uses strict delay times to indicate the end of a transmitted message, which, if not detected, prevents any valid data from being read. When attempting to transmit, the driver is required to monitor the transmission of other ECUs before and during message transmission. Each transmitted byte needs to be looped back to insure proper form on the bus. The open collector topology of these nodes means ECUs can transmit at the same time, mangiling each other’s data.
These unique network requirements make driver development difficult. Failing to act properly on this leads to check engine lights or suboptimal engine performance. Once data collisions are detected on the bus, a reacquisition scheme must be followed.
KeepTruckin has developed its own Linux driver to manage all aspects of interfacing to the SAE J1708 network. Over the years, this driver has been tested on thousands of vehicles through North America. Our embedded team uses data-driven metrics to monitor performance in the field and fine-tune timing where required.
Using data to drive better performance and reliability is the backbone of the KeepTruckin ELD. With more data coming from multiple protocols on ELDs, our software adapts to the bus networks available to ensure the most accurate data available from each vehicle. We have developed proprietary heuristic prioritization methods to choose the most reliable data source for each field required by the mandate.
In this blog, we explained why having access to older network interface technology is key to providing a reliable ELD platform here at KeepTruckin. Without it, critical insights into a fleet’s operations are missed.
In need of tracking a truck older than the SAE J1708 standard? Checkout the KeepTruckin Asset Gateway.
