Code 74 Injector wiring fault HELP!!!

Towmater14 · Oct 2, 2018

YukonTrucker said: ↑

So the engine is an 04 MBN CAT in a KW chassis. We rebuilt the engine and I did an ecm tune from Mr haney, Marine Cam, Turbo, Manifold the works pretty much. Stayed with mbn internals and injectors.

First trip out after the rebuild got the code 74. Brought the truck back in the shop and changed #6 injector. Ran fine for about 1000 miles then gave the code again. This time we found a broken wire on the #6 wiring on the internal harness right by the part that bolts to the injector solenoid so we put the repair kit on and all was good. Did a 3000 miles trip and gave me a code 74 and 73 this time. We found 2 more breaks in the internal injector harness so we replaced it.

Next trip out throws the 74 again. We find the injector wiring hold downs have come loose so we tighten them up and locktite them and at the same time to cover our butts we did jumper wires for the 5 and 6 injectors on the external harness.

The engine ran fine for 10k miles then gives the code 74 again. We can't find anything wrong so we put a new external harness on the truck and change 5 and 6 injectors to rule out the solenoids. After 2 hours of running it gave the code 74 again and since this latest code 74 was coming up we found the engine had to get warmed up before it will throw the code. If the truck is left to cool down it will run fine till it gets warmed up. It will last longer empty than loaded before it throws the code.

We started thinking ecm so we put a different one on and same thing. Our shop, the Kenworth dealership and Finning are all stumped so I am turning to the minds of the forum for help on this I am looking for a direction to take to try and find this gremlin of an electrical problem.

Thanks in advance for any responses.
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Hey, did you ever figure out the problem??? I am having the same problem right now! Any info will be appreciated!! Thanks!

brojamz1 · Aug 28, 2019

I am having the same problem. Can anyone please comment. I am setting in Oklahoma right now just after getting the truck out of the shop. Missing on 4 for the 4th time after 4 inner harnesses 1 outer and 4 ecms and 4 injectors. We finally changed to a 70 pin ecm with the exact same results. Sick of dealing with it. Every new mechanic wants to start by changing the injector. We did that Friday and it ran 60 miles and back to the same old crap as before. Truck is 07 T600 KW w MXS now running a 70 pin with a 2ws 500 setup with brake saver file. VVA’s are backed off and out of the system. Can someone please throw me a bone before I let her run off in a slippery gully somewhere in BFE... Thanks...

Dbolle · Oct 11, 2023

brojamz1 said: ↑

I am having the same problem. Can anyone please comment. I am setting in Oklahoma right now just after getting the truck out of the shop. Missing on 4 for the 4th time after 4 inner harnesses 1 outer and 4 ecms and 4 injectors. We finally changed to a 70 pin ecm with the exact same results. Sick of dealing with it. Every new mechanic wants to start by changing the injector. We did that Friday and it ran 60 miles and back to the same old crap as before. Truck is 07 T600 KW w MXS now running a 70 pin with a 2ws 500 setup with brake saver file. VVA’s are backed off and out of the system. Can someone please throw me a bone before I let her run off in a slippery gully somewhere in BFE... Thanks...
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Were you ever able to figure this issue out? I’m running into same issue right now.

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