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Doug Barnowski
Doug Barnowski,
Category: Medium and Heavy Trucks
Satisfied Customers: 6
Experience:  HD Truck Mechanic at VIP Truck Center, LLC
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I have 2004 dm690s Mack with a code 128 231 8 Sid, I know it

Customer Question

I have 2004 dm690s Mack with a code 128 231 8 Sid , I know it for j1939 data link, abnormal frequency pulse. Width, or period. I check the plugs and the wire harness. On one of the wire for j1939, there is a .8 ohms drop. Is this enough to cause the code
Submitted: 17 days ago.
Category: Medium and Heavy Trucks
Customer: replied 17 days ago.
Also the J3 VECU connectors pin #17 is slowing a ground where I think it should be a 12v plus from accessory relay
Customer: replied 17 days ago.
I'm beginning to think that maybe the engine electronic control unit or the vehicle electronic control unit maybe failing
Expert:  Doug Barnowski replied 17 days ago.

Hi, my name is ***** *****

On the code the MID 128 is engine, the SID 231 IS THE J1939 control circuit, FMI 8 is electrical fault. So the engine is saying it can't talk to other ECM's or it can't hear them. The twisted green and yellow wires are the data link (J1939) circuit. I need you to check these wires in the inside cab diag plug. The pins are labeled "C" & "D". with the key off and using a multi meter in the ohms position you should have 60 ohms. If you have more or less there is a fault in that circuit, either a green or yellow wire rubbed thru or broken wire or another faulty ECM is interrupting the circuit. It's a hard job but most likely it's outside of the bulkhead and you have to trace the 2 wires from the pass thru at bulkhead all the way to the Engine ECU. You have to take time and inspect very carefully.

The VECU & EECU either work or they don't, there is nothing in the middle.

I hoped this will help you and please rate my help for you today,

Thank You,


Customer: replied 15 days ago.
Hi Doug
I check the data link wire (j1939) from the vecu to the eecu. I did find a plug that that may have been the problem and fix it, but I now getting 120 ohms reading at the vecu plug on those two wire. After I fix the plug and restarted the truck, the code reader reported even more code. The list as forward.
487 8 spn Engine 1 no text available
510 8 spn engine 1 no text available
510 4 spn engine 1 voltage below normal
506 8 spn engine 1 control head
105 5 spn engine intake manifold temp
100 4 spn oil pressure voltage
174 5 spn fuel tempI pulled apart the wire harness, check it and rewape it. Still the same code.
I also clean and check the fuse box.
The only thing left maybe, is to replace the eecu, I think.
Expert:  Doug Barnowski replied 15 days ago.


Now if you have 120 ohms on the data link there is a resister missing. It looks like a gray plug the has no wires coming out of it. It plugs into the j1939 harness in the fuse & relay center. So there is a twisted yellow & green wires with a plug with nothing plugged into it. thats where the resister goes. Its about 1 inch long and gray. Sometimes they don't clip and fall out. See if you can find it or go to the dealer and buy one. There needs to be 2 of them in the circuit, 1 in eecu and one in fuse & relay center. Thats how we get 60 ohms in the circuit. That is the first step and has to be corrected before starting on anything else.

Customer: replied 12 days ago.
I have look and look for those resister, but I can't find any of them or where they would go.
Expert:  Doug Barnowski replied 12 days ago.

This is what the terminating resister looks like. Its light gray and about 1 inch long and about 1/4 inch wide.

Expert:  Doug Barnowski replied 12 days ago.

It should be in with all the wiring and fuses and relays.

Expert:  Doug Barnowski replied 12 days ago.

Here is the locations of the newer style resisters, I will send a picture of the new style resisters

Expert:  Doug Barnowski replied 12 days ago.

new style resister

Expert:  Doug Barnowski replied 12 days ago.

I'm not sure which style you have in this truck. It's near the time that they changed over.

Customer: replied 10 days ago.
Hi Doug, thank you for staying with me on this.
I still could not find anything that look like a resister in the dash. But I did find two plug that look like it coming out of the front of the bulkhead, they are about 12" apart. On the same two wire. I have order a new one.
Customer: replied 8 days ago.
I have a another truck with some problem that I need help with. It's a 1995 CH 613 Mack with a EM7 300 engine. The active code is 128 025 7. My code reader said External engine protection input mechanical system not responding properly. I can not find any info on this in my books. I also have a code of 128 020 7. Something about timing actuator mechanical system not responding properly. On that, I have replace the econovance solenoid valve. But I still have the same problem.

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