Freightliner M2 Flashing signal lights

In this video i just want to talk to you about this 2006 freightliner M2 "Business Class" model truck. This truck came into the shop, the right front low beam light and all of the turn signals (except front headlight turn signals) were flashing at all times even when the truck was shut off and the key was removed. The only way the driver could get the lights to sop flashing was to remove fuse 17 & 19 which are the CHASSIS CONTROL MODULE fuses.
Now after hours of reading and investigation figuring out theory and operation of this lighting system and wiring circuitry i was able to understand how the system was supposed to function, you see the BULKHEAD MODULE located on the drivers side of the firewall is the main brain of the electrical system and receives a lot of the input signals from the switches and sensors on the truck and then relays those inputs as messages on can network J1939 to other modules which in this case was the CHASSIS CONTROL MODULE. Now as a failsafe design by freightliner engineers they have programmed the software of the BULKHEAD MODULE to control the left low beam headlight bulb and the CHASSIS CONTROL MODULE controls the right low beam headlight bulb in the event that one of the modules were to become inoperable for whatever reason than the driver of the truck would have at least one light in operation during nighttime driving. The issue at hand ended up being a compromised CAN network line between the BULKHEAD MODULE and the CHASSIS MODULE resulting in the right side low beam bulb becoming activated and also almost all of the signal light began to flash.
The area of concern was located at the transmission housing on the drivers side of the truck where the wiring harness runs across from the frame to the transmission housing where the wiring had rubbed through overtime and compromised the wirings insulation.
If you are having this issue check that location, if no damage can be found than you may want to perform a resistance check on the yellow and green network lines that run from both modules, expect to see 0.40 to 0.78 OHM's of resistance. When i inspected the wiring i had found that the green network line was 210.90 OHM's of resistance which is wayyy to much.

[@taylorlown5225]

Wow this video is nearly spot on for me, new bulkhead module and new chassis module, my issue is intermittent. Right headlight and flashers start, but have no reverse lights, no high beams, no wipers, no suspension dump while this is happening. Then it will just stop having the issue for a few weeks. No mechanic has been able to find the issue because it stops doing it whenever i get to a shop. I tell them its wiring but they always want to throw parts at it.

[@taylorlown5225]

Forgot to add I lose all my gauges as well and def light starts flashing, I did find some light corrosion on one of the pins to the chassis module when I was changing it out might have to have a new plug installed.

[@Tech-28]

I almost guarantee you have an intermittent short circuit taking down the communications between modules

[@taylorlown5225]

Yeah trying to track it down is impossible it seems, 4 shops and $2500 no solution yet

[@Tech-28]

@@taylorlown5225 :( that’s too bad, I feel bad for you

[@PrabhjotSandhu-tm9yu]

@@taylorlown5225if you still haven't fix it I can help you by sending a wiring diagram.

[@davidwilliam8134]

Mine is doing the exact same thing! Thanks for the video

[@Tech-28]

Hey! Glad to help, let us know what you end up finding, the more information on this video really helps everyone else pinpoint common failure locations on the truck! Thanks and best of luck to you Dave

[@302StangBoss]

My right side turn signal was not working. It was the instrument panel relay or plug. I did put in a new switch but it was the instrument cluster

[@Tech-28]

@@302StangBoss hey thanks for the input!

[@peteriannucci6108]

Sept 5 730pm. Well crap wish i had seen this 2 weeks ago. Have an m2 112. Engine shut off due to low coolant but also the light thing. My mechanic wouldn’t touch it because of freightliner wiring. Dealership found corrosion in plug In cab module to a tune of $2800. So thank you awesome video for next time

[@Tech-28]

hey wish i could have helped you sooner, looks like your truck had issues a week before mine. yeah i will be posting any videos of any issues that arise on our fleet of trucks, thanks for the comment.

[@GregFeeney392]

Great video😊

[@chapo7261]

🙏🏼thank you so much for the advice I just fix my lights I have the same problem , I was on the road yesterday everybody gets mad 😠 because my lights ☕️

[@Tech-28]

Glad to hear the video was a help and that you got your issue resolved :) we need more heavy truck information available to the public

[@KillaJayGaming]

Could this fix my strobe lights from opt switch 1?

[@user-de7su5zz5b]

Tengo un problema con un M2, cuando abro la puerta se encienden las luces delanteras y las direccionales traseras.

[@tommybikes717]

Great info thanks question.. did you ever had hot air coming under the dash area.. steering wheel area while driving on a highway and then almost nothing at a full stop ? 2023 Freightliner M2 Tow truck. Thanks

[@Tech-28]

@@tommybikes717 no I can’t say I have but by the sounds of it your truck may have a hole somewhere in the firewall, sometimes rubber grommets get removed for service work and the mechanic forgets to install it again and hot air from the engine compartment will leak into the cab as you drive down the road

[@tommybikes717]

@@Tech-28 Thanks so much check in tomorrow morning. I’ll keep you posted.

[@Tech-28]

@@tommybikes717 sweet, yeah let me know what you find, I used smoke from an evap test machine once to find a hole in the firewall like that, turned out someone left the shifter cable boot off after changing the cables

[@tdiraketa]

How’s it goin?! helping my buddy, pretty much same set up, I think 2012. what did you have to do to fix the problem? Was it just removing the green from ground? Thanks.

[@Tech-28]

It was a rubbed through wire in the harness that cause the wire to turn green. In the CAN HiGH network line “green in color”

[@tdiraketa]

@@Tech-28 thanks. gonna go look at that spot now. have same symptoms. Resistance all over the place with ecu plugged in. with it un plugged I get 60 on green and yellow.

[@Tech-28]

@@tdiraketa yes the ecm will add a bunch of resistance to the circuit, 60 ohms is a lot and maybe both green and yellow wires are affected.. definitely get in there with a light and take a good hard look. Let me know what you end up finding, I’m interested

[@sunnysmarket]

Hello I got 2011 freightliner m2 106 . The Signal lights working perfect, everything is working perfect Just the break lights don't working

[@MegaPimp31]

​@@sunnysmarket did figure it out

[@jagvirtoor1137]

Pls tell the location of signal relay

[@Tech-28]

I have no idea Tbh

[@shadymaint1]

I have a M2 in the shop right now. The cab marker lights are flickering at reduced brightness. The rear marker lights do not work at all. Headlights and turn signals all work OK. There is a relay clicking rapidly in the fuse block behind the driver seat. Cab marker lights still flicker with that relay removed. A wiring diagram would be so helpful.

[@Tech-28]

Even with the wiring diagram it’s so poorl laid out by freight liner that it’s stupidly difficult to understand why they wired it that way

[@Mutanthawk80]

Did you ever find a solution for this issue? I’ve got an M2 with an Altec body with the same issue.

[@shadymaint1]

@Mutanthawk80 I found the wire for the marker lights above the rear roll up door pinched at the top of the door. Wire was shorted to ground. Repaired the bad spot in the wire and zip tied it out of the way. All better.

[@shadymaint1]

​@Tech-28 found the problem. Wire for the marker lights above the rear roll up door were pinched in the door.

[@Tech-28]

@@shadymaint1 beauty! Nice work.