Need a gut check before replacing ECM - CAT 277B (Aux Hydraulics not working)

[Shoe3669]

I picked up a new to me CAT 277B with only 1,300 hours on it, but unfortunately aux hydraulics and 2-speed are not working.

I’ve chased the aux hydraulic problem, and have found the following:

Proportional switch is functional when testing duty cycle at ECM input, Pin # 53. Range from 50% at neutral to 20% and 80% when rolling the wheel forwards and backwards. I believe this confirms that the switch and wiring are sound.

I confirmed continuity between A1 and A2 solenoids and ECM, pins 40 and 58. Believe wiring is sound between solenoids and ECM.

With cab raised and key switched to ON, not running, I do not have any duty cycle signal at Pin 40 or 58 at ECM. I believe this confirms that ECM is toast…anything I might be missing? Any chance the machine needs to be running to get signal through the ECM from the proportional switch to the A1/2 solenoids?

Thanks!

 

[heymccall]

Running, and pilot enabled, would be my educated guess.

 

[Rob1325]

Make sure seat and door safety switches activated when testing

 

[Nige]

Any chance the machine needs to be running to get signal through the ECM from the proportional switch to the A1/2 solenoids?

As mentioned above, yes, because the engine RPM signal is also an input into the ECM. Zero RPM, systems they no worky.....

 

[Mobiltech]

Have you checked for power supply to ecm?
Possible blown fuse.
I would want someone with et to verify no communication or faults.

 

[Shoe3669]

Have you checked for power supply to ecm?
Possible blown fuse.
I would want someone with et to verify no communication or faults.

Yes, I’ve confirmed power to the ECM.


I will re-check signal to solenoids with cab lowered, door shut, etc.

Also of note, when I click the RH joystick trigger button (continuous flow, I think), I can hear the hydraulics cycling on and off intermittently…sometimes they stay activated and won’t turn off when re-clicking the trigger button, other times the trigger button doesn’t do anything at all.

 

[Nige]

Also of note, when I click the RH joystick trigger button (continuous flow, I think),

No it ain't. It's just the actuation for the AUX. If you want continuous flow you have to press two push buttons one after the other.



If you don't have an Operation & Maintenance Manual already then you really need to make getting one a priority.

 

[Shoe3669]

One more data point - pin #40 (A1 Solenoid output) at ECM has 9.1v power when machine is running. Duty cycle reads 88% when moving the thumb wheel, no change in any position. When the RH joystick trigger switch is activated the hydraulics audibly work (still intermittently) and the voltage changes to 9.5v, and the meter reads 61% duty cycle.

 

[Nige]

I agree with @Mobiltech. You really need someone with ET to ensure you have full communication and check for the presence of any Active Codes.

 

[Shoe3669]

I’ll load it up and take it to the dealer Tuesday to see if they can read it.

 

[Nige]

I’ll load it up and take it to the dealer Tuesday to see if they can read it.

If you do that have them download a Product Status Report (PSR) in pdf format before they mess with anything then another one when they finish up. That will give you a good idea what the situation is regarding the health of the machine.

 

[Shoe3669]

If you do that have them download a Product Status Report (PSR) in pdf format before they mess with anything then another one when they finish up. That will give you a good idea what the situation is regarding the health of the machine.

Thanks, maybe they will think I know what I’m talking about!

 

[Nige]

Thanks, maybe they will think I know what I’m talking about!

If you ask them to do that it will demonstrate that you know more than most customers..........

 

[Joe H]

And if they say "You want a what?" you're in the wrong place.

Joe H

 

[Shoe3669]

Alright, took it to the CAT dealer and they hooked it up to ET. The only thing definitive that the tech found was that the RH Joystick trigger button was throwing a low-voltage error. He didn’t see anything else that stood out. When I described the checking/testing that I had already done, he said it sure sounded like a problem with the ECM. I will note that he did not start the machine when hooked up to ET, only turned the key on.

Oh, and I forgot to ask for the PSR!

 

[Nige]

I will note that he did not start the machine when hooked up to ET, only turned the key on.

That's all he needs to do. The Communication Adapter between the machine and his laptop needs machine power to fire it up.

The only thing definitive that the tech found was that the RH Joystick trigger button was throwing a low-voltage error.

Do you mean the 2-speed trigger.? If so see the attachment.

 

[Shoe3669]

That's all he needs to do. The Communication Adapter between the machine and his laptop needs machine power to fire it up.

Do you mean the 2-speed trigger.? If so see the attachment.

It was on the Right joystick, which according to the schematic would be “work tool trigger”

He did test the trigger button on the Left joystick and did not find any problem there.

So even though the schematic I attached shows only two wires going to the work tool trigger, my machine has 3, I’ve also attached that pic.

 

[Nige]

It was on the Right joystick, which according to the schematic would be “work tool trigger”

Sorry, my bad. Wrong joystick. Can you ask what the Code was that he found.? Makes it easier to look up.

 

[Nige]

So even though the schematic I attached shows only two wires going to the work tool trigger, my machine has 3,

Trace the 3 wires back to the 12-pin connector. Does one of them (the orange one perchance) go into a pin on the joystick side that has no corresponding wire in the machine side of the connector.?

 

[Shoe3669]

Trace the 3 wires back to the 12-pin connector. Does one of them (the orange one perchance) go into a pin on the joystick side that has no corresponding wire in the machine side of the connector.?

Thanks, I will open it back up Friday and see.

I bought another 277B at an auction that just happens to be ~30 minutes outside of my travel route tomorrow, so I am going to pick that one up and see if swapping in the ECM from the new machine effects any change in the one I'm working on. If it does, then I know it's the ECM...assuming its that simple to swap them out and no dealer re-programming is required.

Fingers crossed the new one has working aux hydraulics...