J1939 datalink terminating resistor location

Due to the many configurations and options available, the terminating resistor can be found in multiple locations (250k only vehicles)

• Near the top of the transmission in the Powertrain Harness
• Left frame rail (could be as far forward as the steer tire in some applications) in the Center Chassis Harness
• Left frame rail (near the radiator bracket) in the Forward Chassis Harness (*if equipped with Forward Radar)
• Under the bunk in the sleeper (when factory pre-wired for telematics)
• Near the ACM

 

Old qualcomm wiring still left on the truck from previous owner? Check back of truck, roof line for old wiring still hanging with green, corroded wiring ends.

 

When tesing data link J 1939 do you have truck off with batteries disconnected?
What is the range on Volvo VNL? Is it 60 Omhs?
How do you test individual wiring? Do you unplug part of the harnes from both ends and that measure yellow and green wires?

 

You don't need to disconnect batteries, but it is best that all modules are turned off or in a state of "sleep" mode. Most modules are in sleep mode after 5 mins of key off. All 1939 will have a standard of about 60 ohms, including Volvo. Datalinks are about the most tricky to troubleshoot and test. But, yes, can still test conventionally green to green and yellow to yellow end to end for broken or shorted wires.

 

All tested fine. Terminating resistor on the top of the fuses tested 119.6 Ohms. Second couldn't be tested since it's embed into Engine ECU.
Diagnostic port J1939 pins C and D tested 59.8 Ohms. It is mysterious data link issue for sure.
Had problems shifting but they usually disappear once I show up at the mechanic or once I come back home(live in Chicagoland so it might be temperature dependent since it's always cold in Chicago.
Data link codes are intermittent and showing in truck diagnostics for
*Engine
*Transmission
*Vehicle ECU.
All Data link codes
Data Erratic..
Tonight none existant. Go figure..
So far changed TCU, one speed sensor, and inspected all the wiring to the best of my knowledge. My mechanic did the same ..
He said main problem is that this is not active at all times..

 

Yes, this is why datalinks are so frustrating and difficult to repair. The problem has to be constantly active to troubleshoot. If not, you are literally looking for a needle in a haystack. Could be a wiring problem, or a module problem. If you are getting around 60 ohms, your datalink is good. That is normal.