Case Alpha series EH control drive solenoids voltages

[aknetman]

I'm working on an Case sv185 with EH controls that is throwing code 4754
"Right Swashplate angle sensor - Implausible command, command does not match with swashplate angle"
Symptoms include no reverse on the right side.
I looked in the service manual for code 4754 and it basically has you verify that all drive solenoids and swash sensors are plugged in correctly.
-I replaced the swash angle sensor to no avail.

-Tested drive solenoids resistance - 3 are at 6.2 ohms and one is at 5.7 ohms. I'm assuming that they are all ok but don't see reference values to compare against.

Each drive solenoid has 2 wires, a white one(pin 1) and a blue one(pin 2). All lead to the UCM. I am seeing voltage on both wires on the solenoids. According to the manual see below, blue wires should be path to ground, but I am showing 6k or 10k ohms between blue wire and chassis ground with the battery switch off. Also, these blue wires from the UCM are showing anywhere from 7.5v to 12v (depending on how many solenoids are connected) when powered up.

Check for proper resistance in the ground circuit by using a multi-meter to check for continuity between connector
X-16 pin 2 and ground.
A. If there is continuity, continue with step 5.
B. If there is no continuity, there is an open in the ground circuit. Use Frames 26 and 27 to troubleshoot and
isolate the faulty wire.

Any pointers on what normal voltages should be on these solenoids would be really appreciated.

 

[aknetman]

Seems to be loose connection on the reference ground from both swash sensors pin 1 through splice #124 back to ucm pin 26 on cn2a. Now to find the splice... not sure where to start looking. The reference ground splice is 6-way and is shared with EHF transducer, control valve sensor grounds, UJM sensor grounds.

 

[aknetman]

Turns out my voltmeter leads were messing with me, wiring is testing ok now...

Serial Number is NBM443628
Here are the current symptoms: (machine is on blocks so wheels can spin safely)

The left side turns faster than right. This happens in both ISO and H. Moving the joystick just off it's seat (Forward or reverse)will spin the left wheels, but the right side you need to move the joystick more like an inch to get the same RPM. Running with or without high speed (rabbit) engaged makes no difference on joystick sensitivity difference between Left and Right side.

Still getting code 4754 once in a while. Seems to happen when right side is moving reverse? The brake slams on when it throws the code and does not sound good. The right swash sensor is reading 2.5v (+-.1v) in neutral position.

I'm starting to think that the spool on the right pump may have an issue.

 

[92U 3406]

Code is set when wheel movement is detected with no drive solenoids energized or if the wheel movement is in the opposite direction of the energized solenoid.

I would check the solenoids to see if any of them power up when they aren't supposed to.

If you find and fix the fault and it is still mistracking you may need to have the drive and joysticks calibrated. Don't believe calibrations can be completed with active faults on it though. As time goes on and hydraulic components and joysticks wear they need the calibrated values updated to run correctly.

 

[aknetman]

Thanks for the reply. I'm thinking that if I am in ISO mode then only a single joystick signal is used to command both Left and Right sides to drive in the same direction and should see identical readings at the coils..

 

[92U 3406]

I haven't dove that far into the EH systems as of yet but I'd imagine the values should be relatively close but probably not exact. That's what the calibrations do, compensate for variences between the 2 sides so they drive straight and true. If the pump or motor on one side is a little lazier than the other then I'm thinking you might see higher voltage on that side to even it out.

Take the above with a grain of salt though. Like I said I haven't dove too far into these systems either.

 

[aknetman]

I have pulled and tested the UCM. I am getting 20k resistance on the RH ua2 Y sensor output to UCM ground(CN1A-1).
Here is the test from the book:

Check for a short in the UCM. Completely power down the UCM by removing all six connectors. Using a multimeter, check for resistance between UCM pins CN3A-24 and CN1A-1. A. If resistance is around 99.6 K Ω, continue with step 7. B. If resistance is 0 Ω, the UCM has shorted internally. Replace the UCM. C. If resistance is greater than 200 K Ω, the UCM has opened internally. Replace the UCM.

I am getting a correct (99.5k) resistance reading on the other RH ua1 Y sensor output.
Here is the test from the book:

Check for a short in the UCM. Completely power down the UCM by removing all six connectors. Using a multimeter, check for resistance between UCM pins CN4A-17 and CN1A-1. A. If resistance is about 99.5 K Ω, continue with step 13. B. If resistance is 0 Ω, the UCM has shorted internally. Replace the UCM. C. If resistance is greater than 150 K Ω, the UCM has opened internally. Replace the UCM.

This discrepancy seems to correlate to the right side driving slower than the left.
I do not want to replace the UCM if it is not the root cause of the issue ( or does not fix the issue), but it seems to me that the only option is to replace the UCM.
Edit:
Also found one ground pin with 2k resistance to pin1 ground. It is CN1A-7. All others have zero resistance to pin1 ground.