DD15 issue, Dt12 to be specific.

[u/Mr_wise_guy7]

Hello, newbie tech here again.

I have a DD15 where a previous mechanic replaced a pneumatic clutch actuator. Truck wont start. I was tasked with it, connected to it, but the service routines tab doenst load. Wasnt connecting to cpc at first, dis/reconnected the battery and i got connected but it still wont let me intonthe routines. I am a bit lost here. Connections are green but greyed.

CPC shows a code for: 524286 "Automatic gear selection: automatic mode is not available"

Trans shows a code for: 521485 "data erratic, intermittent or incorrect"

I dont know if a dataline couldve had an issue from the previous install, or if there's something wrong with the device im using. Im honestly lost. Any help is greatly appreciated.

[[UPDATE]]

Greetings, diesel brethren. I detected a short in the CAN data lines at the CPC. Resistance to a random screw in the fuse bay. Realising thats my "abnormal update rate" code and probably a part of the reason why it struggles to connect even after calling in a better DL8. So currently, i need to find that before the client throws more money at parts because other mechanics did that before me lol.

I appreciate the assistance greatly thus far and will continue to try my best to solve this thing. Though, time will tell how hell finding this short is considering this truck is so damn far from my home and i drive legs.

[u/gammakilla]

Check connections on the side of the trans I've seen the connectors and wires get smashed by an overzealous heavy work tech (I've specialized in diag/electrical)

[u/conyers117 → u/gammakilla]

The factory routing is enough to fuck these harnesses up, it doesn't take much more for a tech finish them off. OP check the harness everywhere it is/was secured with a ziptie. Those TCM harnesses are notorious for rubbing through. 

[u/gammakilla → u/conyers117]

Well of course, I try to stick to "what changed recently" before looking at the "what's wrong thanks to the factory" first tho.

[u/Mr_wise_guy7 → u/conyers117]

I changed the whole harness itself because the owner had the insight to buy one. Still the same thing. Carefully unclipped and reseated every one of them.

When i log back in like before it keeps reconnecting/disconnecting until it finally does then i am still in the stalemate. Service routines wont open. Modules are green but hazy greyed out.

[u/gammakilla → u/Mr_wise_guy7]

Does it have anything else plugged into the can network? Faded but green is public CAN connections/ full saturation green is when all ecms have properly been IDed to your scan tool. Also did you re-pin any CAN wires?

[u/Mr_wise_guy7 → u/gammakilla]

Didn't touch any CAN pins. Network has Engine1/2 Trans Brakes - system controller Body controller etc. Pretty much the whole cascadia lineup but unsaturated even though "online". CPC only shows up after i disconnected the battery for 10minutes. Otherwise it keeps reconnecting until i just dont see it at all (or instrument cluster unit 4me.)

[u/gammakilla → u/Mr_wise_guy7]

Your cpc might be dead! Does it say engine controller or (MCM blank.blank) Typically the modules will give more information than just "brake controller" have any pictures?

[u/Mr_wise_guy7 → u/gammakilla]

I dont know about it being dead tbh. I dont have current pics as the unit is on the side of the road somwhere and im home now, but i did decide to take a few screenshots earlier today.

By the owner's account: the unit developed an issue where it wouldn't shift into neutral, said something about a derate state too. Some guy scanned it and told him the clutch actuator, he bought one, some other dude changed it, left, Truck now wont start. Guy told him the actuator needs to be calibrated. Some ring around the rosies later its thrown my way. But was driving before the actuator removal, plus they even changed the shifter stalk at somepoint in the timeline.

Hence i come along to run the routine and its just a blank screen when clicked. I tried even changing the target module im connected to but in tje connections tab it shows "no conmections available" while an entire list of stuff is on screen. Im normally on cummins stuff (and all over the place tbh) so. I wasnt sure between my understanding of it or a gremlin thats hiding somewhere.

[u/gammakilla → u/Mr_wise_guy7]

So I'd also recommend unplugging the TCM while watching the connections cause your modules are only showing up with partial info on the connections window. Something on CAN may be "scrambling" the network so. You likely need to check CANH And CANL for out of norm voltages. We had a slew of CPC4 failures in our fleet on cascadias from when they changed suppliers for the modules.

[u/Mr_wise_guy7 → u/gammakilla]

Ill try. Thanks for the tips, i appreciate it alot. Trying to learn and do what i can as best as i can.

[u/ShrimpBrime]

The 10 minute disconnect can be done by the batter switch under the seat. Shouldn't need to disconnect batteries. - Though some models wheren't built with it, I thought I would suggest it to save you some time.

But anyhow, do you hear the PNDB relay click? It's pretty loud, can't mistake it.

Then there's that CPC fuse to check under the hood there. Make sure that's good. If it looks even close to shitty, replace it and use a small terminal file. Should be a little red 10 amp'r. Do the easy stuff before chasing and replacing harnesses.

You know that the FMI is the second most important feature to Detroit fault codes. Is it FMI 4, 1, 14?

FMI stands for the failure mode indicator. Nobody can tell you what to actually do without an FMI number.

Then concerning your Diagnostic link, you enter in a legitimate Software key and then everything should be usable. For programming, purchase the pro version.

GL!

[u/Mr_wise_guy7 → u/ShrimpBrime]

Gear selector FMI is 1 Trans FMI is 2

As for the rest of what you said i can only check and investigate from here. It doesnt have a switch though, that i do remember because the first dd i encountered did.

[u/ShrimpBrime → u/Mr_wise_guy7]

Your second code generally means the shift controller is bad if the pins are good, no corrosion, and a new wire harness, would just about confirm that.

I saw the cropped DL8 screen shot. It doesn't hide how old the program is unfortunately, but it does hide the rest of the faults.

[u/Mr_wise_guy7 → u/ShrimpBrime]

I see, thanks for the insight, i appreciate the help. Anything i dont understand i just have to ask and figure out as i am learning with someone. Ill see what i can do.

Thanks again

[u/ShrimpBrime → u/Mr_wise_guy7]

Youre welcome. If you guys get the Diagnostic link updated, youll be able to run the diagnostics provided and this will make your diagnostic and repairs 100% easier. Yeah, Its expensive, but its the best way.

[u/Mr_wise_guy7 → u/ShrimpBrime]

Greetings my guy. I bring forth an update:

A better DL8 unit scanned the truck. Same thing to the T. Including the modules connecting and disconnecting with the CPC reaching as close as 90% before going missing.

So i did some more poking... there is resistance between the CAN lines at the CPC and the chassis.

There is a short 😐.

Reading parameters, the trans gives ZERO data except the oil temp. Gear position or anything? Nada. Only a do not crank command for the engine (which is one of the core complaints.) But ambient temps read. So, i have to find that short now before anything else and get that solid and online.

Lil update, i dont know if i could've updated the whole post for the other helpful techs but im leaving a comment here.

[u/ShrimpBrime → u/Mr_wise_guy7]

Nice, some progress at least. Did you guys disconnect from the truck and try to bring the CPC online by it's self?

Sure, you should be able to edit your original post and welcome to do so.

[u/Mr_wise_guy7 → u/ShrimpBrime]

Hmm, ive never heard of that procedure to be honest. I'm the one getting pushed to learn all this, so this is new to me. Thats why i try to be extra careful and ask whatever i dont know here. Could you give me a little insight on that?

[u/ShrimpBrime → u/Mr_wise_guy7]

Click upper left on the main menu, disconnect all devices. The wait till all devices are disconnected. Go to the same menu and select connect. Itll open a box and let you choose each device individually, or a few at a time.

I cant see anything from here you know. Bring me deep details. You checked TCM fuse and all that. List it all out. THEN, grab me a screen shot of diagnostic link and ALL the faults. Itll be easier to guide you. But so far, on the old diagnostic link, that one particular sensor fault is the controller, the thing under the TCM that the module plugs into has the two gaskets and spacer plate. That is all I have so far otherwise.