Technologies

[Ronald1951]

I have fault code showing J1939 data communication loss on 3 of 4 ECMs. Bridge port ECM reads OK. If I plug bridge portside cable into bridge starboard side ECM, then bridge starboard side ECM reads OK. So it is not ECM but I suppose it to be a cable problem. Down in pilothouse, neither ECM reads but since neither one comes up I cannot cross check as I did on bridge. So I am ssuming it is some connection problme somewhere in cable. Or perhaps some battery feed not getting to 3 of the 4 ECMs??? We opened the Deutsch 40 pin connectors in engine room and also connectors behind ECM units and they seemed clean so we just added some anti-corrosion block.

What else to try to find the problem????

Thanks for anything to try.

RA

[Mariotall]

Is it a new installation ?

If not, check the continuity in your J1939 wire between the ECM and Bridge. You must have any resistance in this wires. Make the same test with a Wiggle test in ET.

Your problem look a intermittent problem....

[dave10010]

Did you swap the bridge MPD connectors? If the stbd display worked plugged into the port connector, you have a display problem. Is this a new installation? Have you checked the termination resistors? The resistance between the data link wires should be 60 ohms. If resistance is 120 ohms, a termination resistor is missing.

[BlackCat1]

The port and starboard J1939 networks are electrically isolated so treat each one separately.  J1939 networks require two 120 ohm terminating resistors at the far ends of the network to operate properly.  To test, turn off power to the MPDs and engines then make sure all other connectors are connected.  Unplug the 12 pin connector to one of the MPDs.  Test for resistance between pins 7 and 8.  60 ohms +/- 5 ohms is good.  120 ohms indicates only one terminating resistor is installed.   Anything much higher or lower is an indication of wiring problem. 

If the MPDs turn on and show “J1939 data communication loss” then the power is OK to the MPDs.  The MPD will show this message if the engine ECM have the Keyswitch or DC power turned off while the MPD are powered up.