New Holland backhoe all-wheel steering fault

Rusty Owner/Technician Oakham, Massachusetts Posted   Latest   Edited  

This 2000 LB-115 backhoe tractor (Unit S/N … is stuck in circle-steer mode. The axles are not, and will not synch. It appears that circle-steer is the default mode as it defaults to circle steer with the control ECU unplugged. The selector switch functions and shifts the mode correctly on the display but the indicator remains blinking indicating that it cannot complete the mode change. I'm told that the fuse for the brake switch and AWS system has blown intermittently but today it would not blow and the ECU has power and ground.

This module has been replaced (updated) some years ago prior to being purchased by the current owner.

I'm handicapped as I lack a legible and understandable wiring diagram. I have some S/I and was able to identify what each of the 8 and 12 pins in the 2 ECU plugs are for. It seems as though we have no B+ to the steering solenoids above the rear axle. When I test for power on the control side of the solenoids on the 4 "EV" circuits in the 8 pin plug, they are all "dead".

My assumption is that I'll be hunting for a chaffed or corroded wire that feeds the solenoids but I'm baffled as to which of the 12 or so wires in the harness going to the solenoid body is the suspect circuit. Knowing that, I can apply redundant B+ and see if I'm on the right track. Then we did deeper or run an overlay. The harness is extremely difficult to follow and examine.

I do have the translator so I can translate the foreign color-letter designations to English colors but I can't read the diagram as its too fuzzy and there's no continuity between pages. (diagrams are PDFs e-mailed from a cooperative dealer but they are claiming the originals are just as bad) I'm hoping someone here has access to something understandable.

Happy trails,

+4
Chris Diagnostician
Lansdale, Pennsylvania
Chris
 

Rusty, Scott just sent me over here. Give me 15 minutes or so to get on lunch and I'll see what I can do to help you out.

+2 Ð Bounty Awarded
Rusty Owner/Technician
Oakham, Massachusetts
Rusty
 

Take your time. I'm into other things now. I'll go back to the machine anther day when I have better info. I appreciate any assistance but again, no rush on my end

0 Ð Bounty Awarded
Chris Diagnostician
Lansdale, Pennsylvania
Chris
 

Rusty, Shoot me an email at … - I have everything you should need. Thanks

0 Ð Bounty Awarded
Chris Diagnostician
Lansdale, Pennsylvania
Chris
 

I'm going to post up the process Rusty and I went through, and he can add on when he has the opportunity. He was able to get the problem resolved. I had the factory SI for the machine and so Rusty and I begin examining the diagrams and the theory of operation. Through theory of operation, some schematic reading, and a good dose of logic we were able to drill down to a test plan that seemed it…

+5 Ð Bounty Awarded
Rusty Owner/Technician
Oakham, Massachusetts
Rusty
   

This machine is fixed. A replacement front "alignment sensor" solved the problem. As you can see in the photo Chris put up, the wiring was a mess where the 3 wires entered the sensor body. It wasn't obvious until some diagnostics let me to suspect that the sensor circuit was at issue. Once we stripped back the harness jacket, the broken and shorted wires became obvious. Where I took a…

+2 Ð Bounty Awarded