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catmastertech
catmastertech, Technician
Category: Construction and Road Equipment
Satisfied Customers: 2245
Experience:  Field service technician for CAT 19 years.
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My 2003 skid steer model 257 has a park swith issue, it

Customer Question

My 2003 skid steer model 257 has a park swith issue, it constantly stops , so I am having to press the park switch. I hope this can be a simple fix. Thanks
Submitted: 1 year ago.
Category: Construction and Road Equipment
Expert:  catmastertech replied 1 year ago.

Hello,

Try following this guide to find the problem. If you need more help, please post the full machine serial number with your reply.

Solenoid Valve (Parking Brake) Does Not Function Correctly

System Operation Description:

The parking brake solenoid has no diagnostics for checking for faults in the system. The solenoid will NOT be energized when there is an

open circuit or a short to ground. If the parking brake solenoid is shorted to the +battery the solenoid will be ON all the time.

Test Step 1. CHECK FOR HYDROSTATIC OPERATION

Occupy the seat.
Lower the armrest.
Turn the key start switch to the ON position.
Press and release the parking brake switch.
Expected Result:

The hydrostatic system should energize.

Results:

OK - The hydrostatic system energizes. Proceed to Test Step 2.
NOT OK - The hydrostatic system does NOT energize.
Repair: See Troubleshooting, "Switch (Parking Brake)".

Stop.

Test Step 2. CHECK VOLTAGE AT THE SOLENOID VALVE WITH KEY SWITCH OFF

Turn the key start switch to the OFF position.
Locate the parking brake solenoid under the cab.
Disconnect the parking brake solenoid from the electrical connector.
Measure the voltage across the two contacts of the harness connector (A958-WH and 202-BK).
Expected Result:

The voltage should be less than 2 DCV.

Results:

OK - The voltage is less than 2 DCV. Proceed to Test Step 3.
NOT OK - The voltage is greater than 2 DCV.
Repair: The wire harness is shorted to a + battery circuit. Repair the wire harness or replace the wire harness.

Stop.

Test Step 3. CHECK VOLTAGE AT THE SOLENOID VALVE WITH KEY SWITCH ON

Turn the key start switch to the ON position.
Measure the voltage across the two contacts of the harness connector (A958-WH and 202-BK).
Expected Result:

Voltage should be less than 2 DCV.

Results:

OK - The voltage is less than 2 DCV. Proceed to Test Step 4.
NOT OK - The voltage is greater than 2 DCV. Proceed to Test Step 6.
Test Step 4. CHECK THE VOLTAGE AT THE SOLENOID VALVE WHILE THE KEY SWITCH IS ON AND THE PARKING BRAKE IS RELEASED

Turn the key start switch to the ON position. Press and release the parking brake switch.
Note: Two people will need to perform this procedure. One person will need to be sitting in the seat with the armrest in the DOWN position.

Measure the voltage across the two contacts of the harness connector (A958-WH and 202-BK).
Expected Result:

The voltage should be greater than 10 DCV.

Results:

OK - The voltage is greater than 10 DCV. Proceed to Test Step 5.
NOT OK - The voltage is less than 10 DCV. Proceed to Test Step 7.
Test Step 5. CHECK RESISTANCE OF THE SOLENOID

Measure the resistance between the two wires of the parking brake solenoid.
Expected Result:

The resistance should be 10 ± 2 Ohms.

Results:

OK - The resistance is 10 ± 2 Ohms.
Repair: The problem does NOT appear to be electrically related.

Stop.

NOT OK - The resistance is NOT 10 ± 2 Ohms.
Repair: The solenoid has failed. Replace the solenoid.

Stop.

Test Step 6. CHECK THE WIRE HARNESS FOR A SHORT CIRCUIT

Locate the Interlock ECM.
Disconnect the wire harness.
Turn the key start switch to the ON position.
Check the resistance from contact 13 of the wire harness to the following contacts: contact 1, contact 11, contact 24, contact 29, contact

62 and contact 70.
Expected Result:

The resistances should be above 2 Ohms.

Results:

OK - The resistance readings are above 2 Ohms.
Repair: The ECM is unlikely to fail. Terminate this procedure and restart the procedures. Verify all the readings.

Stop.

NOT OK - One or more resistance readings are below 2 Ohms.
Repair: The wire harness has failed. Repair the wire harness or replace the wire harness.

Stop.

Test Step 7. CHECK THE WIRE HARNESS FOR CONTINUITY

Turn the key start switch to the OFF position.
Connect a jumper wire between wires A958-WH and 202-BK on the wire harness at the end of the parking brake solenoid.
Locate the Interlock ECM.
Disconnect the wire harness.
Check the resistance between pin 13 and pin 66 of the wire harness.
Expected Result:

The resistance should be less than 2 Ohms.

Results:

OK - The resistance is less than 2 Ohms.
Repair: The ECM is very unlikely to have failed. 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.Replace the ECM, if the cause of the

diagnostic code was not found after the second attempt. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

Stop.

NOT OK - The resistance is greater than 2 Ohms.
Repair: The wire harness has failed. Repair the wire harness or replace the wire harness.

Stop.

Customer: replied 1 year ago.
thank you very much, the reason i havent read your answer is because i realized that having a weak battery will disrupt several electrical functions. i installed a new battery and problem gone. the info you provided to me will be saved for future issues, thank you
Expert:  catmastertech replied 1 year ago.

Thanks for the reply. Glad you found the problem. Batteries are often neglected as are the cable connections. If I have any complaints about starting, that is where I always begin repairs.

Yes, this document is very helpful for troubleshooting. If you need help at anytime, please feel free to ask for me.

Please remember to rate the answer, it is the only way I get paid from your deposit.

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