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Jeremy, Certified Truck/Bus Technician
Category: Medium and Heavy Trucks
Satisfied Customers: 3375
Experience:  ASE Med/HD Truck Technician, NATEF Diesel Engines and Electrical/Electronics Technician, EPA 608/609 HVAC Certified, Steering/Suspension and ABS/Brakes Technician
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We have a home made system that connects to the J1939 wires

Customer Question

We have a home made system that connects to the J1939 wires at the 9-pin diagnostic connector and can receive and translate the PGN's. How can we read the fault codes? Once we can receive the data from the canbus, we can then interpret the codes>
Barry Nield
Submitted: 2 years ago.
Category: Medium and Heavy Trucks
Expert:  Jeremy replied 2 years ago.
My name is ***** ***** I will assist you. The only way I know how to read the codes on their vehicles is with the Detroit DDDL or Freightliner Service Link software and a adapter. We don't support home made systems on the vehicles. We only support manufacturer authorized systems. Not sure if this is what you are looking for or not. __________________________________________________________________________________________________________________________You want a 5 star service and I want to provide a 5 star service. Please consider that I don't know your skill level as well as I can't see,touch, smell, hear, or taste the vehicle/machine in question. Please provide as much detail as possible and I will provide as much back.The system DOES NOT automatically give me credit from your deposit. A rating is REQUIRED. You are rating me for the information I provide,not the website. I have no control over the site fees, site errors, category errors, or how long it took for a response for these reasons.I am not an employee of this website, so please rate with a POSITIVE (green) rating for me to get credit for assisting you. You still paythe website for negatives or by not rating at all. I just get nothing from that payment you made. So please rate each answer I provide.I want you pleased with my service to you so please inform me before rating negative (red) and I will do my best to make it right. Followups for same question are always free after ratings have been made.I do have many workshop manuals, diagrams, etc that I pay to get access to out of my pocket. If one is needed, please ask and I will giveyou an offer at my technician discounted cost to you for such manuals. I never charge above that cost.Thank you for allowing me to assist you through Just Answer!Jeremy
Customer: replied 2 years ago.
This does not answer my question.
Expert:  Jeremy replied 2 years ago.
I apologize, but there is no other answer to your question. You asked how to read the fault codes and that is how you read them. You use the manufacturer software and a data adapter to do so. I'm not sure what else you need.
Customer: replied 2 years ago.
The question I asked is about what the data stream is for the fault codes. Our electronics connects to the +J1939 and -J1939 wires at the diagnostic 9-pin connector and receives the PGN's from this source. We then select the PGN's we want to get the data from and then convert this data to the values as specified in the engine manual.We want to do this to see when fault codes are transmitted. The question we want answered is do the fault codes transmit on the +J1939 and -J1939 wire connections and, if so, what is required to receive these codes. Are they in the same format as the PGN's or do they have a different format.Barry
Expert:  Jeremy replied 2 years ago.
I understand now. Yes, it communicates throught the + and - sides of the cable. It uses the standard ANCSII 8 bit communication that a PC uses with one big difference. A PC network uses a standard 32 bit addressing table, like what you find with IPv4, and the truck uses a 64 bit addressing table. There are 8 tables with 8 bits each. To help you out a little bit, I will load up the J1939 training info I have that should hopefully help you out a little bit. Just so you know, the question asked is beyond the scope of a technician and more on to the scope of an engineer. I'm a network technician currently training to be an engineer, but I deal more with onboard communications on the vehicle and not via the communications too much between the modules on the truck. I do know how they communicate and understand what they do, but I haven't studied the details of how the engineers have set the communication up. In one of the items I am loading up, there is a Excel spreadsheet that has the addresses for the free publications for the SAE J1939 protocol. They can give the exact SLOT info that you would need to communicate. I unfortunately don't have that for their exact comm link is J1939 and J1939-71 and the side I work with is J1939-73 to communicate via IPv6 and IPv4 side of the application layer so the companies can track the equipment and what it is doing. I did start as a technician on the J1939/J1939-71 but that training is more of what to do if the modules are not communicating, not in the details of how they communicate. Here is the info.
Customer: replied 2 years ago.
Hello Jeremy:That is a big help. The referenced Excel speadsheet did not come through and would appreciate it if you could send again directly to me at***@******.***. Any other info you have would also be appreciated.Thanks,Barry
Expert:  Jeremy replied 2 years ago.
See if it went through this way.
Expert:  Jeremy replied 2 years ago.
I see you viewed my response. Do you need any more assistance on this question?