7 codes J1939 system down

[Rawze]

(08-28-2020 )tree98 Wrote:  Right now it's 120 ohms with the 14 pin connector unplugged and the nox sensor both connected and dis connected. The batteries are disconnected also. I found the terminating resistor in the harness it tests good. Wouldn't the circuit be at 60 ohms if the nox sensor was unplugged or bad?

Check to see if you have 60-ohms at the J1939 connector for that circuit on the can buss wires with everything plugged in (and power off to everything).

It could also be that you are missing a +5-volt supply wire from the ecm to those circuits.... look in quickserv at the engine wiring harness / ecm wiring diagram and see if the supply line is common to those sensors you are having a failure with.

you could also see if you have roughly about 2.5 volts on each of the can buss lines with power turned on using a volt meter. If one of the J1939 buss lines is +5 volts or 0-volts... something is wrong with one of the devices on it.

last, but not least ... you could start unplugging devices one at a time and resetting codes until you only have one fault code (for the device you unplugged) instead of 6 or 7 at a time.