Is it safe to communicate through CAN BUS on a pre equipped tractor?

Hi All,

I am new to CanBus and I am gathering information here and there because a friend of mine asked me if I could have a look at his 3 year old Massey Ferguson which, he said is pre equipped with auto steering. The tractor is supposedly equipped with the appropriate components to be driven by an MF GPS system but it has never been used on this tractor.

On telegram I have been warned I could damage the steering valves if I just plug and command the steering system with AGopenGPS on its CanBus version. I actually already built a Teensy based card from Common Rail’s PCB but did not plug it into the tractor.

Before I do something wrong, I want to ask you if it is doable. Can I run AGopenGPS CanBus version on a tractor which is pre equipped but on which it has never actually been used ?


It’s doable. Plenty of folks here on the forum have done it.

I’m skeptical of claims you can wreck the steering valve by sending bad commands. I don’t physically see how it’s possible for one, and for two CAN and CAN devices are designed to be very robust and fault-tolerant. Both to electrical problems (shorts, etc), and data corruption issues (wrong messages, bad values).

I had one situation where something I did was pulling the CAN voltage down too low and that might have caused my ancient brown box Deere monitor to fail. Or it could have just failed from old age. And of course a wiring harness could have rubbed through somewhere, shorting the wires together as well and I wouldn’t expect ECUs to die from that, so I suspect the failure had nothing to do with what I had done.

Obviously the manufacturers are going to say that connecting to the CAN bus will void warranties, burn your tractor to the ground, damage the engine, cause hair loss, etc. They have a vested interest in keeping you out of the machine that you bought so they can cash more cheques.

Check the thread I made on 6718S, works great, no issues.

You can’t send bad commands to wreck the valve - you can send commands to reconfigure it, but you don’t want to do that. Just follow the guide.

CAN is resilient to accidental gnd/12v so it shouldn’t break it anyway, but your steering valve connects to CAN3. I’ve firmware that can engage autosteer using the headland management button too (CAN1).


Thanks for your replies.

@andyinv I read through your thread and that’s why I am even more motivated right now :slight_smile:

I called my friend who owns the tractor. I got more details. He told me it is autosteer ready but it doesn’t have the antenna and I suppose the GPS receiver and modem neither. So I am wondering if it is really autosteer ready and what does the autosteer ready system include ?

The warnings I got were about sending messages to the canbus on a tractor on which the WAS and the steering valve are not calibrated. I found details about this in the following thread : Massey Ferguson 7700 autosteer ready - Projects - AgOpenGPS
I was told we should take the tractor to the dealer and have him calibrate the steering system. Only then can we send orders to the canbus safely. The risk being to block the steering valves if we keep sending the order to turn left/right when the wheels are already in the max turning angle.

Calibration is always a good idea, I’ve seen some that weren’t and the steer curve wasn’t pretty but you can set AOG not to go full-lock anyway so that’s no risk. The “steer ready” is pretty much the valve appearing on the bus I think. You don’t want a receiver or modem if you’re going AOG.

Sure I don’t want a receiver or a modem. I just thought that maybe the manufacturer equips all tractors with that and then the farmer only pays for the activation…

Ok I see, I should set the max steer angle to a value making sure I don’t go too far and reach the physical maximum value, then AGO will never go past this limit.

We will probably reach the dealer and ask what the calibration would cost. Once calibrated, the max steer angle will be known and saved in the tractor’s ECU so this will result in a native protection against over steering. Am I correct ?

Are you not able to calibrate the WAS yourself? On a Fendt at least you can do it, perhaps all AGCO tractors are not the same. A calibrated WAS is needed for other tasks, also on a tractor that isn’t autosteer equipped.

Sending the command to turn left/right when already the stop is not much different than holding the steering wheel at full lock. It’s very obvious when you do it, and it won’t damage anything.

Edit: I came back to say that leaving it running in that condition for an hour might cause oil to overheat, but on a modern PFC CCLS tractor I don’t think it even would.