Bobcat T770 aux no com and main no com codes

[landworksTN]

I have a 2020 Bobcat T770 that is giving us a couple of intermittent codes. They don’t always come on at the same time but most of the time they do. M4404 aux no communication and also main controller no communication. I can’t remember the code number right off hand with the main controller. When they come on I have no rabbit on the left joystick and the horn won’t blow as well on the same stick and of course no aux power. We have visibly checked all the fuses, relays, connectors, and the harness and don’t see any obvious issues. Does anyone know what might be the cause of this and would the joystick have anything to do with it? Sometimes the aux no com code will come up by itself but the main controller code only comes up after the aux code comes on. Thanks for any help you may have.

 

[ozarkag]

Bad aux controller. Guaranteed. I have 4 bad ones here to prove it,

 

[landworksTN]

I bet you’re right. Is it the one located under the cab in the center mounted upside down?

 

[ozarkag]

One of two under cab on the machines left side. One is the main frame controller, other one with fewer wires is the aux controller. Will require Bobcat tech to program.

 

[jdkrailroad]

Were you able to fix your T770 with an Aux Controller? I have the same two codes and an additional Left Hand panel code on my S650. Dealer can’t diagnose the issue because it’s intermittent. They are trying to sell me on a new controller and eventually a new harness too.

 

[ozarkag]

If you have the aux no comm code, even if intermittent, that is a failing aux controller. Not so much logic or diagnosis as it's a case of a well known problem.

 

[Skid-steer Repair]

Were you able to fix your T770 with an Aux Controller? I have the same two codes and an additional Left Hand panel code on my S650. Dealer can’t diagnose the issue because it’s intermittent. They are trying to sell me on a new controller and eventually a new harness too.

Sounds like the dealer DID diagnose it.

 

[cmarchant45]

I just replaced the aux controller on our t77 skid steer and that was $1200-$1300 just for the part I installed and took it to dealer and paid $120 to program it and after about a week and only using the machine just a couple times and now I’m getting the same m4404 and no aux functions idk any advice other than dropping it off for the dealer to charge me $400k to fix it ?

 

[landworksTN]

Replacing the aux controller on mine fixed my issue but during my research I found that the aux computer is just part of the loop. You could also possibly have a harness issue or one of the joysticks could also be bad and I have heard they are common problems. I have a really good independent mechanic that is really good at diagnosing problems and he was able to find a no communication issue coming out of my aux controller and could pin point it to that. Perhaps you could find a guy like that that could potentially zero out some of the variables to find the problem rather than taking it to one of the incompetent dealers and you just letting them throw money at it. I have a very bad taste in my mouth with bobcat after the issues I’ve had with my skid steer. I’ve spent probably $15k on it this year alone just with repairs and it only has 1800 hours on it. We have zero mobile dealer support here and if you take it to them it sits there for months and they literally just throw parts at it. Our local sunbelt rental has bobcat machines and they can’t even get anything out of the company as far as assistance. We are expanding again soon and I can tell you if won’t be with bobcat machines. Good luck on your issue.

 

[dayrondlt]

Bad aux controller. Guaranteed. I have 4 bad ones here to prove it,

Hello, my bobcat t450 has an intermittent code ( r7404 ) “no communication with main controller " when this code shows up it won’t let me do nothing and after 10 seconds approximately he turns off… if I wait 10 mins or more i can start it again and everything works perfectly but the code comes back again after a few minutes he only do that after 2 hours of working with it approximately…. I checked everything, grounds, alternator and wiring and I don’t see anything wrong. Please if anyone had this sane issue let me knows

 

[ozarkag]

If you do not have the "M4404 Aux no comm code" could be harness/ wires or main controller fault.
If you do have the Aux comm code is a very good possibility that controller is failing.

 

[dayrondlt]

I just have the r7404 code i checked everything and nothing i think that maybe is the main controller but i dont know where is the main controller i have a black box behind the battery and another one on the right side of the engine at the top i think that one is the ecu but im not sure

 

[ozarkag]

Main controller is under cab on left side. Just below where main cab harness comes down. The aux control is beside it, has fewer wires going to it.

 

[dayrondlt]

ohhh ok ok thanks so much i think is the gray one i will post here the pictures so you can see

 

[ozarkag]

Gray 7010248 is that aux Controller. Basically takes care of auxiliary hydraulics, 2 speed and a few more things. The black unit in the last photo could be the main controller. Check for potting or sealant cracks around d the edges.

 

[dayrondlt]

Gray 7010248 is that aux Controller. Basically takes care of auxiliary hydraulics, 2 speed and a few more things. The black unit in the last photo could be the main controller. Check for potting or sealant cracks around d the edges.

I will check tomorrow… i have another controller behind the battery after the fuse box looks similar to the gray one but is black

 

[Mimmo80]

Hy friend,
I have a problem with a bobcat T770, when I press the AUX button no activation light comes on and the tool does not work. Could you help me? Thanks

 

[Mimmo80]

Hy friend,
I have a problem with a bobcat T770, when I press the AUX button no activation light comes on and the tool does not work. Could you help me? Thanks

one more thing, i don't have any fault codes

 

[DCCurtis27]

Hello i have a 2019 Bobcat T870 with only 600'hrs. I am getting a M6604 code and it says no communication with ECU.
I have checked all the connections and grounds.
If I turn the key on the code immediately comes on and will not crank.
One out of 20 times that I turned the key all the way into crank it did crank for me.
Now I'm unable to get it to crank it all.

 

[landworksTN]

Hello i have a 2019 Bobcat T870 with only 600'hrs. I am getting a M6604 code and it says no communication with ECU.
I have checked all the connections and grounds.
If I turn the key on the code immediately comes on and will not crank.
One out of 20 times that I turned the key all the way into crank it did crank for me.
Now I'm unable to get it to crank it all.

I’m no expert on these but to me it sounds like a main controller failure or a harness issue and there’s no communication. I had an independent tech come out when my aux controller failed and he was able to isolate the controller as the problem by checking the harness for communication coming in and out of the controller. This may be something you could try or have a tech verify for you.