Heavy Duty Vehicles Scanner

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Heavy Duty Scanner

Our HD-Scanner is specially developed for Heavy Duty Vehicles, which enables users to read DTCs, clear DTCs and view the data stream with a live bus protocols, such as J1939 and J1708/J1587. So you may hope to learn more about J1939 and J1708/J1587. This paper is about them.

J1939 J1708 J1587 Introduction

SAE J1708, SAE J1587 and SAE J1939 are automotive diagnostic protocol standard developed by Society of Automotive Engineers (SAE). They are used in heavy-duty vehicles  such as trucks and buses, mobile hydraulics, etc. 
In many ways, J1939 is similar to the older J1708 and J1587 standards, but J1939 is built on CAN.

SAE J1708

SAE J1708 is a standard used for serial communications between ECUs on a heavy duty vehicle and also between a computer and the vehicle. With respect to Open System Interconnection model(OSI), J1708 defines the physical layer. Common higher layer protocols that operate on top of J1708 are SAE J1587 and SAE J1922.

SAE J1587

SAE J1587 is an automotive diagnostic protocol standard developed by the Society of Automotive Engineers(SAE) for heavy-duty and medium-duty vehicles built after 1985. The J1587 protocol uses different diagnostic connectors. Up to 1995, individual OEMs used their own connectors. From 1996 to 2001, the 6-pin Deutsch. Some OEMs still use the 6-pin Deutsch. It has mostly been used for US made vehicles and also bt Volvo. 
SAE J1708 makes up the physicaland data link layers while SAE J1587 makes up the transport and application layers with respect to the OSI model. SAE J1587 is ysed in conjunction with SAE J1708 for automobile communication.

SAE J1939

SAE J1939 is the vehicle bus standard used for communication and diagnostics among vehicle components, originally by the car and heavy duty truck industry in the United States. 
SAE J1939 is used in the commercial vehicle area for communication throughout the vehicle. With a different physical layer it is used between the tractor and trailer. This is specified is ISO 11992. 
SAE J1939 can be considered the replacement for the older SAE J1708 and SAE J1587 specifications. 
SAE J1939 has been adopted widely by diesel engine manufacturers. One driving force behind this is the increasing adoption of the engine Electronic Control Unit(ECU), which provides one method of controlling exhaust gas emissions within US and European standards. Consequently, SAE J1939 can now be found in a range of diesel-powered applications: vehicles(on and off road), marine propulsion, power generation and industrial pumping. 
Applications of SAE J1939 now include off-highway, truck, bus and even some passenger car applications.


No. 1: The SAE J1708/J1587 were first released in the middle of 1980s. It is still live and kicking. Some people might wonder: what's so special about J1708/J1587? 
1. First of all, it is the cost. The J1708 hardware is a modified version of RS485 (but it doesn't require terminal resistors) which makes it very cost effective. It is still the cheapest bi-directional protocol in the market. Though the CAN controller and CAN transceiver is getting cheaper and cheaper, the J1708 still gets the best bang for the buck in many situations. 
2. Performance wide, it is not so sad: it uses 9.6K baud rate and can take no less than 20 nodes for up to 40 meters (131 feet). 
3. The serial port/RS485 based design makes it extremely easy to connect with computers for the service/diagnostic purpose with low cost J1708/RS232 converters. 
These three major factors make it a secondary option on Diesel ECM besides the CAN interfaces. The J1939 has been widely used in many North American diesel engine ECMs, the J1708/J1587 is used there too. People start talking about phase out the J1708 interfaces on diesels and trucks, but it might take many years. 

No. 2: How to determine if your heavy-duty vehicles use the J1939 or J1708?  
We don’t have a collection of “network implementation vs. model year” due to the fact it is very complicate matrix and there is no much rule to follow. 
However, the following message may be useful. 
1. Consult with 4S shop to confirm. 
2. Consult with vehicle's manufacturer to confirm. 
3. Send us messages to tell us your vehicle's made and model year. We do have some feedback from our clients, which may help you.
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