Hello all, I have a cat 257b serial # SLK05001 I purchased a while back. I am having trouble with the aux hydraulics for a grapple, etc. This is a high flow machine so it has a thumb wheel. Here is what it is doing: - Pull the thumb wheel down and hydraulics function correctly. With no tool on it labors trying to push oil. - Release thumb wheel and machine keeps laboring. - Push thumb wheel up and it quits. -Pushing up does not make it push oil in other direction. Please note that I DID try replacing the thumb wheel. I was positive that was the problem, and it was not. Luckily CAT let me return an $1150 handle.... I have tested the solenoids on the valve and they both show the same amount of resistance with a multimeter. I have used a test light to verify that the connector to one solenoid is receiving power, but the other is not. Therefore, I have an issue somewhere between the switch harness and the wire that connects to the solenoid. Where should I go next? I saw that there is something in troubleshooting info from cat about what to do if the switch only works in one direction, but I have not been able to find it. Thanks!
Do you have an electrical schematic.? It would probably be useful.
Let me get this right. So rolling the thumbwheel back to the neutral (centre) position does not shut off the AUX hydraulics and you have to roll it all the way in the other direction to get the AUX to shut off.? Have you inspected the electrical connections on the ECM yet.? what sort of condition are they in.?
I have a partial schematic but not the full one. Correct, merely releasing the thumb wheel does not shut it off. I have to go into the other direction or the machine will continue pushing oil. No I have not, where is the ECM located? I got lost tracing the wires through the harness.
I’ll try to find some diagrams of the ECM location and send you a full electrical schematic as well. One of the first tests to do when you have the schematic will be to measure the output voltage from the thumbwheel switch in various positions.
That would be super helpful thank you!
Are you saying you still suspect a switch problem even though I put a new handle and switch on? It still seems like a switch issue except for that, but obviously there is some amount of signal happening when I push the thumb wheel up....
Not necessarily. I was interested to see the switch output and then go to the ECM and confirm that what’s coming out of the switch is actually making it to its destination. EDIT: Here's the chassis wiring. The ECM for the Work Tool Control is #20, mounted in the RH footwell.
Ok thank you that makes sense. Do you have any idea what parameters I should be looking for out of the switch?
Locate the 12-pin connector directly below the joystick. The pin numbers will be moulded on to both halves of the connector. You'll need attachments for your multimeter to measure voltage in the pins without unplugging the connector. With key ON engine OFF measure the voltage between Pins 1 & 2. It should be 8.0 +/- 0.5v. Measure the voltage between Pins 3 & 2 with the thumbwheel switch in the centre, then with it rolled all the way in both directions. Report your findings.
Sorry I failed to mention that the measurements should be repeatable to within +/-0.1v no matter how many times you do them. So for example if the first voltage measurement for the centre position of the thumbwheel is 4.55v then if you measure it a dozen times all the others should be in the range between 4.45 & 4.65v. The same tolerance range applies to the maximum and minimum measurements. Once you have the results at the switch move to the ECM and measure the voltage arriving there on Pins 52 & 53. These are the same wires P996 Green & P997 Brown that come from Pins 2 & 3 of the 12-pin connector at the switch. Again measure 3 positions of the switch and record your results.
Ok I will do that. So you are saying 52 and 53 are the ones going INTO the exam right? Or out of?
Correct. If you follow wire numbers P996 & P997 on the schematic from the thumbwheel switch they go to Pins 52 & 53 of the AUX ECM. We want to make sure the signals are good going INTO the ECM before we start looking more deeply into what's coming out.
ok, we tested as you specified. Pins 2 and 3 deliver: - 4.04-4.09 in center position - 1.9 in down position - 6.28 in up position Testing between pins 52 and 53 I get the exact same numbers with several repetitions and very minimal change. What pins do I use to check coming out of the ecm? Philip
So those numbers confirm that there is nothing wrong with the roller switch or the wiring as far as the ECM and that the required signals are getting to it. On the output side you need to measure between Pins 40 & 42, then between Pins 58 & 42. Pin 42 is common. One of those pairs powers the AUX A1 solenoid and the other pair powers AUX A2. I don't know which way the roller switch has to move to power which pair but I'm sure you'll figure it out. Test with key switch ON, engine OFF. All wiring harness connector remain plugged in. Test both at the ECM end and the solenoid end. Use the wire colours/numbers at the solenoid end to identify which is which. You will need the cab raised for the second test. The AUX solenoids are mounted on opposite ends of the main implement control valve.
Ok these numbers line up with what I am seeing as well. Between 40 and 42 it shows nothing in the center position. When I push the switch down it shows -2.65. When I release the button it does not return to 0. When I push the button up it returns to 0 Between 42 and 58 it shows 0 with the switch in the center position or up position. In the down position it shows a slight negative of -.029 So this means my ecm is bad??
It wouldn't surprise me. Try disconnecting the machine harness connectors A-C24 & A-C25 at the A1 & A2 solenoids and repeat the tests. See if the results change.
Ok I will do that. So you’re saying if it worked differently with those disconnected there could be a solenoid issue right? What is that specific ecm called and what is the part number for it?
Those handles are 1150 dollars now
Potentially yes. while you are in there disconnecting A-C24 & A-C25 also test the resistance of the solenoid coils for A1 & A2. It should be 2.2 ± 0.2 ohms. It's called the Aux Hyd Control ECM and the Part Number I see for it is 216-0658. There may be a newer Part Number than that and there also might be the opportunity for a Reman ECM which would have a Part Number something like 10Rxxxx or 20Rxxxx. You would have to ask your dealer Parts Dept. Before condemning an ECM it's worthwhile doing all the tests that can be thought up, and few more besides, mostly because of the cost. I take it from your OP that the AUX function has never worked since you have owned the machine.?
While you are messing with the A1 & A2 solenoids do you have an external power source you can hook up to each of them in turn with the engine running to see if they work and the hydraulics load up.? Even better if you have an attachment that can be connected hydraulically to the machine. The only problem I have right now is I can't find information regarding the operating voltage of the solenoids, so to be safe I wouldn't recommend applying any more than 6v to them, certainly not battery voltage.
Maybe worth a look at the continues flow switch perhaps the switch is stuck in the pressed position
Tyler makes a good point. Go to the LH handle and open up the 12-pin connector. Check the continuity on Pins 11 & 12 for the Cont Flow switch as you press & release the button.
Continuing on from that........ When you finish testing the Continuous Flow switch, leave the 12-pin disconnected and measure the output between Pins 40, 42, & 58 of the AUX ECM and the input to the A1 & A2 solenoids like you did before. Do you see any change from the previous tests when the thumbwheel is rolled one way then the other.?
Ok so to test this I can have the 12 pin disconnected for both these tests? Or I need to probe from the back and leave them connected?
Correct, the past owner told me it didn’t work and at the time I was not too concerned. He acted like it wasn’t worth fixing for him but wouldn’t say how much he looked into it.
Correct. 1. The 12-pin connector on the LH joystick was dsconnected to confirm that the Continuous Flow push-button switch was working correctly. 2. Leave it disconnected, and turn the key switch ON. 3. Roll the thumbwheel to both extremes while backprobing Pins 40 & 42 then Pins 42 & 58 of the AUX ECM. 4. Repeat Step 3 but measure by backprobing at connectors A-C24 & A-C25 at the solenoid end of the circuit. See if anything changes from what you posted previously........ "Between 40 and 42 it shows nothing in the center position. When I push the switch down it shows -2.65. When I release the button it does not return to 0. When I push the button up it returns to 0 Between 42 and 58 it shows 0 with the switch in the center position or up position. In the down position it shows a slight negative of -.029"
Did you measure the resistance of the A1 & A2 solenoid coils.?
Confirmed that 216-0658 is the latest current Part Number. The Reman Part Number is 10R-5613. But don't go condeming the ECM just yet.........
Cancel that. You can safely apply 12v direct to the coil in order to test them.
Ok I am beyond confused now. Here’s what I found tonight in following your directions: Disconnect the 12 pin connection LH handle and test for continuity on pins 11 and 12. No continuity with the bottom left joystick button pushed or released. Suggests that switch is bad. I did however get a reading of 1.1 volts on those same two pins when I press the top right button. Seems strange? checked voltages coming out of ecm with the above connector disconnected. There was no rhyme or reason to my readings, and rolling the thumb wheel either direction basically had no effect. Plugged the connector back in with the same effects. To the point where I started the machine expecting no function of the thumb wheel at all but acts exactly the same. What would make it be erratic? I checked both solenoids and they both fall within your parameters to be good. I ran out of time to try putting power to them but will tomorrow. I should actually be able to make the function run with that correct? What are your thoughts? I checked and rechecked and don’t understand what made my post ecm readings change.
Provided you were checking on the joystick side of the 12-pin connector rather than the machine side - Confirmed that the Continuous flow switch is not working. Bad news if you ever need it because, like the RH handle, the switch is not available separately. How many buttons does your LH joystick have.? If the coil resistance falls within specification then applying 12v to each of those solenoids in turn should confirm if the hydraulic side of the AUX function is working as intended. If you have an attachment to hook up to the machine so much the better.
Yes, I made sure to test on the side of the plug that would go up to the handle. This machine has 4 buttons left and two buttons and the thumb wheel on the right. Will that switch not working on the left handle affect the thumb wheel though? Yes they tested good. The grapple is on, I will run it and put power off a battery to both the solenoids. Any thoughts on all my early readings though?
No it will not, or at least as far as I know it will not. Based on Tyler's suggestion we wanted to make sure the pushbutton was not giving a signal to the ECM that it was permanently pressed. On your machine Continuous Flow on the AUX system (to save you having to hold the thumbwheel over all the time) is achieved using a combination of inputs from the thumbwheel and the CF pushbutton to engage/disengage. So if your CF pushbutton is non-operational then CF will not work. Good. Initially try powering each of the solenoids in turn with the key ON, engine OFF. You should hear them give a distnct "click" when you power/depower them. If you get that then move on to test them with the engine running. Do this with CARE because by applying power direct you are bypassing all the systems in the machine controls that are designed to keep the operator safe.
Sorry for the delay, I wasn’t able to work on it yesterday. Here’s where I’m at: Took a 12 volt battery and energized both solenoids. One was working the other was not. I took the non working one apart and cleaned it up and that solenoid now works. I started the machine and used my outside power to run the grapple both directions as it should. Then I reconnected everything and tried it. Still only works one direction. Ironically the circuit that is dead is the same circuit that bad solenoid was on. I am going to test one more time to be sure but it still appears that I don’t have power out of the ecm to that one circuit. Is there anything else I should be checking??
A couple of things spring to mind. 1. With the solenoids in their original position swap the wiring between them and test. Does the problem move with the wiring or stay where it is.? 2. Switch the position of the solenoids leaving everything else original wiring-wise, then test again. The results of that should give you an indication if you have bad wiring. You are rapidly exhausting all the possibilities leaving a failed ECM as the only one.
I am having trouble with the function that typically worked acting strange now, I am going to run jumper wires from the ecm to those two solenoids to make sure there isn’t a wire issue between the ecm and the solenoid. Sound like a good idea?
It does to me. That ECM is expensive and mis-diagnosing it as bad could be bad for your wallet, as wel las not fixing the problem.
Ok heres where we’re at: I disconnected the connector at the ecm and used my 12 volt battery to pin 42 and 40, then 42 and 58. Both solenoids function properly so I have determined that the wiring from the ecm to the solenoids is functioning correctly. I also retested and the wiring from the switch to the ecm is working. So unless there is something outside of that simple circuit which affects how the ecm performs….. the ecm is bad. Correct? Now here’s a thought…. This machine is highly optioned with all the different auxiliary line options but all I foresee myself caring about is the main aux circuit to run a grapple and a post hole auger. Could I not take those three wires that run out of the 12 pin connector by the switch, and bypass the ecm with those three completely, just have them run directly to the solenoids? We would leave everything plugged in so the switch would still have power, we would just be eliminating the brain and having the switch power the solenoids directly. I know this would keep things like the continuous flow switch from working, but at this point I don’t care. Is the amount of voltage carried by those wires enough to run the solenoids? I believe pin 1 is the common wire that runs to both, and 2 and 3 would each go to a solenoid. Correct?
And yes I know this is not a fix anyone would probably recommend. I would like to do it in a way that I could easily restore it to factory and replace the ecm down the road but not have to spend $1200 or more right now. Feel free to tell me if I’m totally wrong.
Correct. Unfortunately it will not work. As you measured earlier, the switch output voltage is: - - 4.04-4.09 in center position - 1.9 in down position - 6.28 in up position So if you hook the switch directly to the solenoids they will both be permamently powered. If you don't want to go to the expense of replacing the ECM at this time the only possibility is to unpin the wires 40, 42, & 58 from the ECM connector and wire them via some sort of spring-loaded centre biased toggle switch. You would need a 10A fused power supply to the switch, output would be on wire P978-GN for one solenoid and P979-YL for the other. You would need to connect the L998-OR common wire from both solenoids to machine frame ground. To remove the wires from the ECM connector a Deutsch connector de-pinning tool is required. See this LINK but you can also get them elsewhere. Note that ythese tools are fragile and easy to break if too much force is used. There are plenty of vides on Youtube showing how they are used. De-pinning the ECM connector and retaining the original pins on the wires means you could refit them if you replaced the ECM at some point.
What other functions does that ecm control?
Take a look on Page 13 of the schematic for the full list. Also note that there are certain signals (armrest switch, implement lockout switch) that are integrated with the Interlock ECM that is located right above the AUX ECM on the schematic.
Something that may interest the OP. In conversation with a contact who works for a Cat dealer he offered the information that in his experience the most common failure of the AUX Hyd Ctrl ECM is a loss of response to the thumbwheel switch in one or both directions. Make of that what you will.
Thank you that gives me a little more confidence. I forgot to report back but I bit the bullet and ordered an ECM. $1200 but they do offer returns surprisingly. I am crossing my fingers that fixes it. Even with all our testing I feel nervous!
I'd get that in writing. Usually once you open the box you're done for with ECMs. I reckon that ECM will come without software in it, which you will need. Something to think about.
I have a feeling there will be some sort of cover on the plug that, once tampered with, will void returns. I made sure to buy one preprogrammed, I gave them my machine info so they could program. Crossing my fingers, I will let you know the result!
Most cat ecm’s have a timed test mode . I can’t remember how many hours it is but if you remove it from the machine within those hours it can be returned .
In that case you should be ok.
Hey everyone just wanted to give an update. My new ecm came, I plugged it in, and it works like a dream cause glad our diagnostics panned out! Thanks for your help, hopefully with having the resolution and everything someone else can use this thread to fix theirs. Also just fyi….. a remanufactured ecm from cat was 4000 unprogrammed. I got one from an independent company that works on ecms for $1400 programmed and ready to go. Thanks guys!
If the new ECM works well why not give them a plug and share where you bought it from? Sounds like good value to me. Might help out the next person.