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Dan
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Category: Construction and Road Equipment
Satisfied Customers: 4647
Experience:  17+ yrs. shop and field experience with all major brands of heavy equipment and trucks - 1995 WyoTech graduate.
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We have a 287b cat skid steer with the sk120tr forestry

Customer Question

we have a 287b cat skid steer with the sk120tr forestry model SN- cat0287BEZSA03494. we are having problems running the regular auxillary hydraulics. I need to know possible reasons why we have no functions on the right joystick and also a pdf of the cat repair service manual for this machine. I would like a specific wiring diagram and hydraulic schematic so i can see which solenoids and which relays run the hydraulic valve. thanks
Submitted: 1 month ago.
Category: Construction and Road Equipment
Expert:  catmastertech replied 1 month ago.

Hello,

The first and most common reason for no hydraulic control is the door switch is not working.

Manuals and schematics are copyrighted material and must be purchased from the dealer. Prices range around $1000. (Less than two days in the dealer's shop!)

The B model has a built in diagnostic indicator in the armrest and parking brake lamps. If either or both of these are flashing, this indicates a fault with the interlock ECM. However, if you have an Auxiliary ECM (for high flow and attachments) you can only view fault codes with CAT ET from the dealer.

Have you checked the door switch?

Do you have any flashing lights?

Customer: replied 1 month ago.
No flashing lights. Only one light on which looks to be a hydraulic symbol. Where would the door safety switch be located at? All other functions seem to be working properly.
Expert:  catmastertech replied 1 month ago.

The switch is on the hinged side and has a harness hanging down to disconnect the door if removed. A bypass plug should be tied to the harness to allow the control to function without a door. You can try the bypass plug to see if the switch is the issue.

You also have a LOCKOUT switch in the console. This could cause a problem but, it is very rare for the switch to fail. If is more common to have a wiring problem.

The hydraulic symbol you are seeing is indicating the hydraulics are off and this could be from either switch.

Expert:  catmastertech replied 1 month ago.

Here is some addition troubleshooting you can perform to find the issue with the work tool control.

Work Tool Does Not Function

System Operation Description:

The Interlock ECM will NOT engage the work tool pilot solenoid if problems exist with the parking brake switch or the work tool pilot solenoid.

Note: Use a jumper wire on machines that do NOT use a lockout switch for the work tool. The jumper wire is 165-0312 Wire Assembly . This jumper wire is fastened to the harness in place of the switch. The jumper must be connected in order to allow both the primary work tool and the auxiliary work tool to operate.

Test Step 1. CHECK THE FAULT INDICATORS

  1. Occupy the seat.

 

  1. Lower the armrest.

 

  1. Turn the key start switch to the ON position.

 

  1. Press and release the parking brake switch.

Expected Result:

The armrest indicator and the parking brake indicator should be off.

Results:

  • OK - The armrest indicator and the parking brake indicator are off. Proceed to Test Step 2.

     

  • NOT OK - The parking brake indicator remains on.

    Repair: See Troubleshooting, "Switch (Parking Brake)".

    STOP

Test Step 2. CHECK THE CIRCUIT OF THE WORK TOOL PILOT SOLENOID

  1. Turn the key start switch to the OFF position.

 

  1. Raise the cab. See Operation and Maintenance Manual, "Cab Tilting".

 

  1. Locate the interlock ECM. The interlock ECM is located on the left side of the machine beneath the access cover on the floor of the machine.

 

  1. Remove the wire harness from the ECM.

 

  1. Measure the resistance from contact 24 to contact 68 (wire P988-OR to wire 975-WH) of the wire harness connector.

Expected Result:

The resistance should be approximately 6 Ohms.

Results:

  • OK - The resistance is approximately 6 Ohms.

    Repair: ECM failure is unlikely. Reconnect all connections and visually inspect the wire harness. Verify that the diagnostic code still exists. If the diagnostic code still exists perform the Test Steps again.Prior to replacing an ECM, contact the Technical Communicator (TC) at your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time and expense.
    If the ECM must be replaced, refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

    STOP

  • NOT OK - The resistance is not approximately 6 Ohms. Proceed to Test Step 3.

Test Step 3. CHECK THE RESISTANCE OF THE WORK TOOL PILOT SOLENOID

  1. Locate the work tool pilot solenoid.

 

  1. Disconnect the wire harness from the work tool pilot solenoid.

 

  1. Measure the resistance of the two wires on the work tool pilot solenoid.

Expected Result:

The resistance should be approximately 10.5 Ohms.

Results:

  • OK - The resistance is approximately 10.5 Ohms. Proceed to Test Step 4.

     

  • NOT OK - The resistance is not approximately 10.5 Ohms.

    Repair: The solenoid has failed. Replace the coil.

    STOP

Test Step 4. CHECK THE RESISTANCE OF THE WORK TOOL DETENT COIL

  1. Locate the work tool detent coil. The detent coil is located beneath the right-hand joystick. Remove the access panel in order to get to the connector.

 

  1. Disconnect the wire harness from the work tool detent coil .

 

  1. Measure the resistance of the two wires on the work tool detent coil.

Expected Result:

The nominal resistance for the work tool detent coil, at a temperature of 25° C (77° F), is 29 Ohms. (Approximately 54 to 60 Ohms is typical)

Results:

  • OK - The coil resistance is within specification.

    Repair: The wire harness has failed. Repair the wire harness and/or the connector or replace the wire harness and/or the connector.

    STOP

  • NOT OK - The coil resistance is Not within specification.

    Repair: The work tool detent coil has failed. Replace the work tool detent coil.

    STOP

  •  

Expert:  catmastertech replied 1 month ago.

The detent coil and the pilot solenoid has been an issue with some machines. This has been the problem I found on some recent repairs I have done and may also be a cause for your trouble.

I will be away for the rest of the day but, can help further tonight with I return. My access to the internet will be limited so, any reply maybe delayed.

Please let me know what you find and how I can help you further.

Expert:  catmastertech replied 1 month ago.

I did find a simple schematic I can send you, it covers the basics of the interlock wiring.

Customer: replied 1 month ago.
When I send 12v to the solenoids on top of the valve body I can get the grapple to open and close
Expert:  catmastertech replied 1 month ago.

Great, you know the solenoid to the control valve work and are not a problem.

What were the results of the testing I sent you?

Did you record the values found in each step?

Customer: replied 1 month ago.
The solenoid beneath the right hand d joystick reads 10.8 ohms. It doesn't say where the pilot solenoid is to check the ohms there
Expert:  catmastertech replied 1 month ago.

Did you measure the resistance from the interlock ECM first?

Customer: replied 1 month ago.
Is the interlock ECM neer the fuse box? I just got this machine and havnt recieved any cat manuals yet so I have no idea where anything is located
Customer: replied 1 month ago.
I've got the cab raised and do not see it
Expert:  catmastertech replied 1 month ago.

The interlock ECM is under the floor plate and to the left side of the machine. (If equipped) The auxiliary ECM is on the right side, under the floor plate.

Expert:  catmastertech replied 1 month ago.

The pilot solenoid is with the right joystick. You will see the same wires connected to it as in the test from the interlock ecm connector. (P988 and 975)

NOTE; the OR means orange and the WH means white color wires.

Expert:  catmastertech replied 1 month ago.

The work tool detent coil also has the same wires connected but the coil is located at the top side and is used to help hold the joystick in the float position when using float.

(Almost none of them are actually strong enough to hold the joystick though and this is were I find the most failures.)

The pilot solenoid is on the bottom of the joystick valve and is a coil and solenoid valve assembly.

Expert:  catmastertech replied 1 month ago.

See the attached image.

#2 is the detent coil (172-0970 COIL AS(12-VDC))

# 3-4 is the pilot solenoid (195-9700 VALVE GP-SOLENOID (12-VOLT)(WORK TOOL))

Customer: replied 1 month ago.
OK the detent is at 55 and the pilot is at 10.5
Customer: replied 1 month ago.
Those were in the front of the machine are those the ECM?
Expert:  catmastertech replied 1 month ago.

Yes, that is the interlock and auxiliary ECMs.

Expert:  catmastertech replied 1 month ago.

You will need to connect the coil and the solenoid and disconnect the ecm harness to preform the test in step #2.

If you do not get the results indicated you have a wiring problem. (OPEN, SHORT depending on your readings.)

Customer: replied 1 month ago.
I don't know if I'm not making great contact or what but I can't get it to make any ohms between those pics
Customer: replied 1 month ago.
Pins
Expert:  catmastertech replied 1 month ago.

Verify the wire numbers and colors to be certain you are on the right circuit. (Some schematics and books are not up to date)

Then disconnect the coil and solenoid and perform a continuity test on the orange wire and white wire to see which one is broken.

NOTE; the white wire is a COMMON return wire and is connected to other circuits. You cannot just bypass this wire or they other functions will not work.

You can try a temporary jumper but, a new harness may be needed

Customer: replied 1 month ago.
I got it to read 8.6 ohms
Expert:  catmastertech replied 1 month ago.

Ok, that is close enough. That circuit should be good.

You have two possible problems. You could have found a bad connection and when you assemble everything, it will work correctly.

Or, you have an issue still with the door switch or lockout switch.

It is possible and not that uncommon to have a failed Interlock ECM. The recommended practice is to place your ECM into a working machine and see if the problem follows the ECM.

A new REMAN ECM will still set you back over $700 and it is not returnable.

I would test the armrest, seat switch, lockout switch and door switch harnesses first and if you have a friend, try your ECM into their machine.

At a last option, then try the replacing the ECM

Customer: replied 1 month ago.
All other functions work, if one of those switches are bad wouldn't it stop me from using other functions.
Expert:  catmastertech replied 1 month ago.

Yes, but when I cannot find a cause for the problem, I retest everything.

The only indicator you have is the hydraulic lamp on.

I am assuming you are seeing light #7 on. See attached image

Implement Lockout (7) - This alert indicator will light when the implement lockout control is activated.

Expert:  catmastertech replied 1 month ago.

I would focus first on the door and lockout switch and then check the other items.

Anything is possible and should be checked before throwing $700 at it.

Expert:  catmastertech replied 1 month ago.

The first image is the right panel, the one below is the left panel.

Expert:  catmastertech replied 1 month ago.

Hydraulic Oil Temperature (1) - This alert indicator will light and an audible alert will sound when the temperature of the hydraulic oil is too high. If this indicator comes on, stop the machine immediately. Stop the engine and investigate the problem.

Engine Coolant (2) - This alert indicator will light and an audible alert will sound when the engine coolant temperature is too high. If this alert indicator comes on, stop the machine immediately. Stop the engine and investigate the cause.

Engine Oil Pressure (3) - This alert indicator will light and an audible alert will sound when the engine oil pressure is low. If this alert indicator comes on, stop the machine immediately. Stop the engine and investigate the cause.

Hydraulic Oil Filter (4) - This indicator will light when the hydraulic oil filter is not functioning properly. Stop the machine and replace the oil filter. The indicator will stay on until the hydraulic oil has warmed up. Do not operate the machine until the light turns off.

Seat and Armrest (5) - This alert indicator will light when the armrest is in the RAISED position. The alert indicator will light when the operator gets out of the operator seat. The alert indicator should go out when the operator is in the operator seat and the armrest is in the LOWERED position.

Parking Brake (6) - This alert indicator will light when the parking brake is engaged. The alert indicator should come on during start-up. The alert indicator should go out when the parking brake is disengaged.

Implement Lockout (7) - This alert indicator will light when the implement lockout control is activated.

Interlock Override (8) - This alert indicator will light when interlock override is activated.

Charging System (9) - This alert indicator will light if there is a malfunction in the electrical system. If this alert indicator comes on, the system voltage is too high for normal machine operation or too low for normal machine operation.

If electrical loads are high and the engine speed is near low idle, increase the engine speed to high idle. This will generate more output from the alternator. If the alert indicator for the electrical system turns off within one minute, the electrical system is probably operating in a normal manner. However, the electrical system may be overloaded during periods of low engine speeds.

Increase the engine idle speed with the governor lever in order to compensate for a higher electrical load on the system.

If this procedure does not cause the alert indicator to turn off, move to a convenient location. Investigate the cause (loose alternator belt, broken alternator belt, faulty batteries, etc).

Engine Air Filter (10) - This alert indicator will light if the engine air filter becomes restricted.

Rabbit Mode (11) - This alert indicator will light when rabbit mode is selected with the two-speed control.

Machine Security System (12) - This alert indicator will light when the machine security system is activated.

Customer: replied 1 month ago.
Thanks you for everything. Ill figure something out. If you happen to have the address of the electrical engineer that designed this system id like to put a flaming bag of dogshit on his doorstep.
Customer: replied 1 month ago.
Actually it is number 4 that is on
Expert:  catmastertech replied 1 month ago.

I agree with you on the engineers. The C model is worse as it has more electronics and you must have the advanced monitor or you cannot view anything. The D model has simple monitor that can do some but, you need the advanced monitor to view the complete codes.

Your auxiliary ecm and all the C models must be tested using CAT ET or you are just shooting in the dark, guessing what might fix it.

I wish they would just keep it as simple as possible. Seems every time we turn around a new scheme is up to change all that used to work just fine.

#4 is just the filter If the oil is cold, it will be on. If it stays on after the machine is warm then you may have a plugged filter? (That could be a whole other ballgame!)

So, that point us back to the door switch or its wiring if no other lights are on.

Expert:  catmastertech replied 1 month ago.

The door switch is connected to the lockout switch at white wire E917. This wire is to ground when the door is closed.

The jumper wire at the 6 pin connector for the door harness is from pin 4 (E917) to pin 2 (200) black wire. Install the jumper to close the circuit and testing the lockout circuit.

NOTE, 200 Black is a chassis ground. Always verify grounds are returning to the frame and/or battery.

Expert:  catmastertech replied 1 month ago.

Switch (Hydraulic Lockout)

Test Step 1. CHECK FOR PROPER OPERATION

Occupy the seat.
Place the armrest in the DOWN position.
Turn the key start switch to the ON position.
Place the hydraulic lockout switch in the OFF position.
Shut the door.
Press and release the parking brake switch.
Expected Result:

The work tool should function.

Results:

OK - The work tool is functioning. Proceed to Test Step 2.
NOT OK - The work tool does not function and the parking brake indicator is off. Proceed to Test Step 5.
NOT OK - The work tool does not function and the parking brake indicator is on.
Repair: See Troubleshooting, "Switch (Parking Brake)".

STOP

NOT OK - The work tool does not function and the parking brake indicator is flashing.
Repair: See Troubleshooting, "Parking Brake Indicator Is Flashing ".

STOP

Test Step 2. CHECK FOR PROPER OPERATION

Press and release the hydraulic lockout switch.
Expected Result:

The work tool should not function.

Results:

OK - The work tool does not function.
Repair: There is no problem at this time.

STOP

NOT OK - The work tool is functioning. Proceed to Test Step 3.
Test Step 3. CHECK THE CIRCUIT FOR THE HYDRAULIC LOCKOUT SWITCH

Place the hydraulic lockout switch in the ON position.
Turn the key start switch to the OFF position.
Note: Ensure that the door to the cab is closed. This will complete the circuit from the door switch to the hydraulic lockout switch. If the door is NOT mounted to the machine, ensure that the jumper is installed in the circuit.

Raise the cab. See Operation and Maintenance Manual, "Cab Tilting".
Locate the interlock ECM. The interlock ECM is located on the left side of the machine beneath the access cover on the floor of the machine.
Disconnect the wire harness from the ECM.
Measure the resistance from contact 60 to contact 3 (wire E918-GN to wire 201-BK) on the wire harness connector.
Expected Result:

The resistance should be greater than 3000 Ohms.

Results:

OK - The resistance is greater than 3000 Ohms.
Repair: The ECM is very unlikely to have failed. Reconnect all connections and visually inspect the wire harness. Verify that the problem still exists. If the problem still exists, perform the Test Steps again.Replace the ECM, if the cause of the problem was not found after the second attempt. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

STOP

NOT OK - The resistance is less than 3000 Ohms. Proceed to Test Step 4.
Test Step 4. CHECK THE HYDRAULIC LOCKOUT SWITCH

Lower the cab.
Remove the hydraulic lockout switch.
Disconnect the wire harness from the switch.
Place the switch in the ON position.
Measure the resistance from terminal 3 to terminal 5 of the hydraulic lockout switch.
Expected Result:

The resistance should be greater than 5000 Ohms.

Results:

OK - The resistance is greater than 5000 Ohms.
Repair: The wire harness has a short. Repair the wire harness and/or the connector or replace the wire harness and/or the connector.

STOP

NOT OK - The resistance is not greater than 5000 Ohms.
Repair: The hydraulic lockout switch has failed. Replace the switch.

STOP

Test Step 5. CHECK THE CIRCUIT FOR THE HYDRAULIC LOCKOUT SWITCH

Turn the key start switch to the OFF position.
Raise the cab. See Operation and Maintenance Manual, "Cab Tilting".
Locate the interlock ECM. The interlock ECM is located on the left side of the machine beneath the access cover on the floor of the machine.
Disconnect the wire harness from the ECM.
Measure the resistance from contact 60 to contact 3 (wire E918-GN to wire 201-BK) on the wire harness connector.
Expected Result:

The resistance should be less than 5 Ohms.

Results:

OK - The resistance is less than 5 Ohms.
Repair: The ECM is very unlikely to have failed. Reconnect all connections and visually inspect the wire harness. Verify that the problem still exists. If the problem still exists, perform the Test Steps again.Replace the ECM, if the cause of the problem was not found after the second attempt. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

STOP

NOT OK - The resistance is greater than 5 Ohms. Proceed to Test Step 6.
Test Step 6. CHECK THE HYDRAULIC LOCKOUT SWITCH

Lower the cab.
Remove the hydraulic lockout switch.
Disconnect the wire harness from the switch.
Place the switch in the OFF position.
Measure the resistance from terminal 1 to terminal 2 of the hydraulic lockout switch.
Expected Result:

The resistance should be less than 5 Ohms.

Results:

OK - The resistance is less than 5 Ohms.
Repair: The wire harness has an open. Repair the wire harness and/or the connector or replace the wire harness and/or the connector.

STOP

NOT OK - The resistance is not less than 5 Ohms.
Repair: The switch has failed. Replace the switch.

STOP

Expert:  catmastertech replied 1 month ago.

Follow the above testing guide EXACTLY as it says and let me know your findings.

If you have any questions please let me know.

I am assuming you battery voltage is correct and you are not jumpstarting this machine.

Low charging or a bad battery can cause all kinds of weird issues.

Customer: replied 1 month ago.
it did test out at 4 ohms
Expert:  catmastertech replied 1 month ago.

Ok, how did the results of the other tests end?

Have you connected all the harnesses and tried to operate the machine again?

Customer: replied 1 month ago.
I connected everything. There was already a jumper wire from pin 2 to 4 . Do you know what the black and purple wire goes to off the same harness as the door switch?
Expert:  catmastertech replied 1 month ago.

That is the lead for a washer bottle pump.

So, I assume the machine still has the same issue?

I would repeat the Work Tool Does Not Function - Test and follow it exactly.

If you repeat the test twice and end with the same results twice, you should have your answer.

If that is stating the ECM has failed, it is time to find a spare or try your Interlock ECM into another machine.

Or, purchase a REMAN ECM.

You have checked everything in the system. The only other suggestion is to try applying battery voltage to right joystick solenoid to see if it will work.

I have not see one stick before but, I guess it could happen. You could swap it with the one on the left side to see if it is a problem. This solenoid is the component that sends the pressure oil to the joystick pilot valves and they send the oil to the main control valve to operate lift and tilt functions.

Customer: replied 1 month ago.
I have lift and tilt functions just no tool function. Is there a way to bypass the ECM and send power to the controller. I tested the controller is seems to be closing circuits
Customer: replied 1 month ago.
I guess I'll just have to replace the ecm
Expert:  catmastertech replied 1 month ago.

Well, I have been totally wasting our time. I assumed when you said you had no functions on the right joystick, that meant the lift and tilt are not working.

The problem from here is your trouble is in the Auxiliary ECM. It has no diagnostic functions you can check. This must be tested using CAT ET program and normally, the dealer is the only source.

Expert:  catmastertech replied 1 month ago.

Since I cannot help you, i will OPT-OUT.

If you wish, you can ask customer service for a full refund.

Expert:  Dan replied 1 month ago.

Hi Cody, There is a customer version of Cat ET you could likely get your hands on but will likely exceed the cost of your repair. Some independent shops do have Cat ET and some contractors with fleets if you know someone that might be able to connect your machine to ET. Otherwise the dealer is your only option but the Flash files for the ECMs are programmed by the dealer and they have exclusive rights unfortunately.

Customer: replied 1 month ago.
Do you know the ECM part number? And is it possible I have the wrong joystick on this machine. I know there was two options
Customer: replied 1 month ago.
I tested the plug at the joystick on the machine side. Brown wire 997 is grounded. The blue wire 994 isn't getting any voltage with the machine running/parking brake off. I also noticed this joystick only has 4 wires and none of them correspond with that blue wire. The green wire reads .3 and drops to .2 when I got the left button on joystick
Expert:  Dan replied 1 month ago.

Hi Cody, I put together some info for you. Click on this link to access the troubleshooting help. This should give you everything you need minus the ability to troubleshoot with Cat ET software.

Troubleshooting

Expert:  Dan replied 1 month ago.

Hi Cody, Did you get this resolved? Please take a moment and rate my service as that is how the site credits my time for helping on the site.