JD 700k CAN resistance

[Midnightmoon]

while testing CAN resistamce on a 700K it appears the can resistors are electeonically controlled by the ECM on that given CAN network but i need confirmation.

while testing resistance at the dash display the display has 50 ohms when unplugged and the wiring to it acted odd. 1.7ohms with power off unpluged from display but if i cycle the power on then off it has 120 ohms a few seconds after it powers off with display disconnected then goes back to 1.7 ohms. is this normal? it appears display risistance should be 120 and the display is bad because if it has a resistor 50 ohms means its bad but maybe jd is a different beast. can anyone confirm?

 

[Midnightmoon]

sn 1t0700kxvee255611

 

[mg2361]

No, that is not normal. What do you measure at pins C and D at the diagnostic (Service Advisor) connector with all controllers plugged in?

This machine have an EH control valve?

Check your PM.

 

[Midnightmoon]

testing at r3 with resistor out i get 1.7ohms key off. cycle the key and for a moment i have 120ohms then back to 1.7. Where is the second resistor? with resistor in at r3 i never have 60 ohms. I suspect 2nd resistor is bad but where is it? John deere tech had no clue but he thought it must be in the display. My guess its in the eh controller but need confirmation. Machine has eh controller. Would you agree display is not on the same CAN as IGC? IGC can is my issue and if my problem arises again I can proove a bad resistor in the eh controller or wherever the resistor is, by putting a can resistor to pins J and H at diagnostic connector. J and H is a different can network from c and d. The j and h is my issue and attaches to r3

 

[Birken Vogt]

Is there voltage coming on the bus when you turn the key on? That would make any resistance reading invalid.

I know nothing about this machine, but is the bus more or less a line? Can you look around the far end for where the second resistor should be?

 

[mg2361]

Would you agree display is not on the same CAN as IGC?

Correct. What issue are you having with the IGC? What codes are active?

The theory of operation for the IGC CAN network only mentions one terminating resistor in the circuit. It does not show a second in the schematics, nor does it mention about any imbedded in a controller (for example, the second Engine CAN resistor is inside the ECU). I'll have to dig a little to see if I can find out.

I can proove a bad resistor in the eh controller or wherever the resistor is, by putting a can resistor to pins J and H

So, if I am interpreting this correctly, if you add a resistor to J and H, your issues go away?

 

[Midnightmoon]

issue is igc resistance and voltage are off an h and low are 1.7 volts and resistance is crap a 1ohm but when you cycle key it pops up to 120 for a moment then crashes back to 1ohm. there has ro be 2 resistors in the igc r3 is good but can network is well.......unhealthy

 

[Midnightmoon]

eh controller has to have a resistor in my mind and on this machine its junk

 

[mg2361]

Both CAN voltages are 1.7 volts? That would be too low.

Are there active codes? And what are they?

If you unplug the EH controller and measure the ohms between the controller's pins 10 and ground and then 11 and ground, what do you have?

There is no TOPCON or other grade control connected to it currently, correct?

 

[Midnightmoon]

of course it has gps control. Im the gps tech my system is fine. With my system disconnected these are my readings. JD is blaming the gps system and I showed JD tech its not my system. The jd side is the issue. I suspect the eh controller as well is 10 and 11 can high and low? I could realy use the full electrical schematic.

 

[Midnightmoon]

4 codes but only one relevant. Non are active only past codes. (SDM 3156.9) (ECU 97.3) (SDM 2141.9) (SDM 3156.9) SDM 3156.9 Loss of can comm with ehc. I suspect when my GPS system is working at full capacity its overloading the IGC network and JD lack of proper resistance cant handle it and crashes. GPS system is not the issue when its complete removed from the JD system machine resistance and can voltage is all wrong. Systems will work with no resistors as long as there is low communication on the network but will be flakey from time to time.

My only real question in this thread is electronically controlled can resistors are a thing in the industry and I need to confirm if deere uses them and where is the second resistor in the IGC CAN network.

 

[mg2361]

Now we are getting somewhere. I'll send you some information on that code through the PM. I would ignore the serial number break.

electronically controlled can resistors are a thing in the industry and I need to confirm if deere uses them

Not that I am aware of in. their C&F products. They did in the AG, but did away with them due to reliability issues.

Complete machine schematics are basically not easy to print in a complete form. I think Deere does that on purpose to make sharing extremely difficult. I'll see what I can do. Again, look for it in the PM.