Electrical Problem

Alright everyone, here is a brain teaser for you electrical guys. Here is what I have going on. Have a 2002 Freightliner Century with a Cummins N14 Celect Plus. I have a few problems and working through it. This truck has been bullet proof until now. When the driver drives the truck the truck will run very good. When we hook it up to a trailer, it will intermittently run like crap. like you turn half the injectors off. the Freightliner dash information center will go dim and act up on him. Than the problem will go away and the truck runs fine. But only happens with the trailer on.

I do have a number 6 injector that is going bad, but this would not make the truck miss like it is, I mean it runs like half the injectors are going bad. No solenoids like an ISX. Also this only happens when a trailer is hooked up to it. We have replaced the trailer pigtail, no change. Sure I have a short somewhere. We do have a bad turn signal we are replacing today, as it is bad. Tail lights are also out now. Also throwing no codes.

Here is what we are going to do Monday. Replace the turn signal switch. Not sure if it can short out the circuit, but needs replaced anyways as it wont hold in certain position. Also the truck tail lights went out today.
Next we are going to the trailer plug on the truck and replace it to make sure it is not shorting on the inside.or any corrosion in there. Going to check the circuit breakers and replace, to make sure we do not have a weak one. Going to down load the electrical schematic to see where the ground is make sure it is clean. We have also cleaned the ground to the from the battery, and cleaned up the battery supply to the ECM.
Wondering if anyone has seen this problem before and what they did to fix it. Thanks.

 

Haven't started the repair yet. Everyone including myself all have plans for Easter Sunday. The reason for the turn signal switch is that it is bad anyways. Doesn't hold in turn positions and so on. Also all the lights do go through the switch, so just hoping even though I doubt it will fix the problem.

It does it with any trailer. Driver did tel me yesterday that if he turns the lights off the problem goes away. Also yesterday the tail lights on the truck went out. Hoping I find a short there or in the 7 way plug on the truck side or pig tail on the truck side.. What it is looking like more and more. I have already cleaned all the grounds at the starter and frame. I did not know about the one location of the ground on the kick panel, thanks for the info. I knew there had to be one for the dash somewhere. I cleaned all the grounds and cleaned up the wiring for the computer supply back at the batteries, and all the grounds up front on the frame and starter.

Will clean the ground on the kick panel, as I like to know my grounds are clean, because they can cause so many gremlins in these newer trucks. Thinking the problem is going to be a bad ground on the tail lights that just showed itself or in the plug or harness on the truck side. I already replaced the 7 way cable that connect the truck and trailer.

I will make sure to post the fix in here so others will know what I found.

 

Here is the answer. The tail lights were a broken wire in the harness. Easy find and fix. The engine information center going dim and the truck running like crap when it did it was the turn signal. It was sending information to the information center to warn of turn signal on. The turn signal switch had a short to ground. The information center is connected to the ECM, which was causing the problem.

I did look at the wiring schematic to check the fix also. It had the problem on any trailer. We hooked up to two trailers and worked perfect. I appreciate all the help. Thanks for the information on where the ground is on th kick panel by the clutch. saved me a lot of time looking,