299d2 emissions computer not communicating

[hvguy]

Long story short, I thought I had the dreaded DEF manifold failure, but come to find out after replacing with the new unit, my tech was unable to communicate with the emissions computer, the DEF gauge says faulted in red. I guess this is what its pertaining to, there are no other codes or anything in the computer.

Anyone ever had this issue? I checked all the fuses, unplugged and plugged in the computer, I even switched it out from another known machine that I had on rent.

Also relating to a computer issue, the two relays that are next to the SCR pump system are clicking rapidly at random intervals, upon looking at what they do I believe it goes to the grid heater system? They seem too small tho.

Does this machine have a main body control module like on vehicles?

Here's a simple video of the issue. Relay issue is at 2:45

 

[Per Eriksson]

ACU power supply the def tank manifold
HTR gnd are for the def line heating.
130 and 40 should have good power at all times.
200 chassies ground
C254 and N894 is grounded by the aftertreatment ecm when it wants to turn the relays on.

So check what you are missing or have intermittnt connection on.

 

[Per Eriksson]

Oh, wait.
He couldn't see them aftertreatment at all in ET?
Then check at the ecm.
pin 10, 11, 18, 19 and 29 for power with key on
pin 31, 33 and 50 power at all times
pin 40, 41, 46, 47, 48 and 49 ground

 

[hvguy]

I'll check now. Since I have a rental here with same FD serials, I swapped SCR pump and computer with no luck, swapped brains and it did the same thing with the relays clicking. I bypassed the relay with a jumper and it won't update the advanced display. I don't have ET unfortunately, I was just watching what the tech was saying.

 

[Nige]

When you talk about “main body control unit“ do you mean the Machine ECM.? It’s under the floor, the seat has to come out to get to it.

If an electrical schematic would help you post a Serial Number.

 

[hvguy]

Serial is fd202537
Yes. The ecm behind where you sit. I pulled the cab on both machines and swapped them. Besides hour and maintenance discrepancies, it ran fine but still had the def failure. Gonna check wiring today

 

[Nige]

Sent you an electrical schematic.

 

[hvguy]

Awesome, thanks! Update:
After installing my old scr pump and computer, I was noticing a very VERY quiet buzzing sound coming from the hydraulic block. I pulled the radiator lid, exhaust tip and cover and stuck my head down behind the firewall and couldn't hear anything. I forwarded my attention to the hydraulic manifold with all the solenoids.... Unplugged them all and the sound went away, turned the machine back on and off and the sound was gone. Plugged them back in, and it slowly got louder. The rental machine that's in perfect working order does not do this. I'll look at those schematics.

 

[hvguy]

after tracing those connectors out, it looks like they all go back to the ECM. Also I hear a very fait clicking sound every 1 second coming from the GPS unit, but this is normal from what I read and observe on both machines.

when I swapped computers, I dont recall listening for this buzzing sound and I really dont want to pull that other machines brain out again. Guess its off to the shop.

 

[hvguy]

after tracing those connectors out, it looks like they all go back to the ECM. Also I hear a very fait clicking sound every 1 second coming from the GPS unit, but this is normal from what I read and observe on both machines.

when I swapped computers, I dont recall listening for this buzzing sound and I really dont want to pull that other machines brain out again. Guess its off to the shop.

Not to dig up an old thread, but in case someone has this issue where its not communicating with the scr pump system... My machine had an online fuse that powered the pump assembly and computer, it was corroded and sorta allowing some power through.

Cleaned and replaced, now it works.

 

[Nige]

Do you mean this one.? Wire 130-RP16 RD is the wire that takes unswitched battery power to the DEF pump ECM.
If not I don't see anything marked on the schematic.