Cat 277C Parking Brake Won't Disengage

[Weekend_Warrior]

Good Morning All,

I have a 2010 (maybe 2011) Cat 277C that I bought used 2 years ago. I have since put about 300 hours on the machine. Serial #JWF01830.

Maintenance items I've performed:
- New alternator and battery (2Q 2023)
- Replaced a hydraulic tubing line under the cab due to a pin hole leak (2 weeks ago)
- New fuel/water separator (1 week ago)
- New parking brake switch (yesterday)

The issue I am facing now is very similar to the one from THIS POST. The problem started after I replaced a leaking hydraulic tubing line under the cab. The hydraulic tank was drained in the process, and I went back with hoses instead of new tubing for simplicity's sake. The photo below shows the connections of the line I replaced.



Upon initial startup after the line replacement, the parking brake would not disengage when I pressed the parking brake switch, and I was not able to operate the tracks. The yellow blinking warning light would flash (no sound). However, the hydraulic interlock would clear and I was able to operate the arms and bucket. This went on for a few minutes and then went away and I was able to disengage the parking brake. I figured it was due to air in the hydraulic system and fluid needing to refill the voids I created. I operated the machine for 8 hours that day without any more issues.

The following day I operated the machine for 2 more hours and then the issue came back after I got out of the seat momentarily. I returned to the cab and saw the yellow blinking warning light flashing again. Once again, I was not able to disengage the parking brake, but the hydraulic interlock cleared when I pressed the parking brake switch. I was able to operate my arms and bucket.

Since then, I've replaced the parking brake switch and checked the seat switch for functionality.

I haven't checked fuses but will do that next.

Unfortunately, I do not have the optional display on the right-hand side. I was quoted $160/hr with a 3-hour minimum for a technician to troubleshoot. This only includes labor and would be my last resort. I prefer doing this myself to save costs (post-Christmas guilt) and to learn more about my machine for future maintenance. I don't have any schematics so please share if you have them for this machine.

I am curious if this is related to the hydraulic system being drained and I didn't follow a correct procedure when I refilled it. Or if it's just a coincidence and the problem is from a solenoid, switch, or sensor going out. 2 posts that I've come across on this site indicate that it could be a bad left-hand joystick.

https://www.heavyequipmentforums.co...issue-afraid-i-already-know-the-answer.60031/

https://www.heavyequipmentforums.co...e-solenoid-testing.105457/page-2#post-1183460

If there is a way to bypass the parking brake I would love to learn how as the machine is out on a property that I am currently working on. Moving it back to the home shop to determine the root cause would be much more convenient.

I understand that it will be very difficult to troubleshoot the issue without being able to scan for codes but have learned that the folks on this forum are very knowledgeable and helpful so I hope that you will please help me get this resolved.

Thank you for your time!

 

[Nige]

Unfortunately, I do not have the optional display on the right-hand side.

All is not necessarily lost. Post a photo of your RH panel please.

If there is a way to bypass the parking brake I would love to learn how

There isn't. The issue has to either be fixed or you will have to resort to dragging the machine.

 

[Weekend_Warrior]

All is not necessarily lost. Post a photo of your RH panel please.

There isn't. The issue has to either be fixed or you will have to resort to dragging the machine.

Thank you for the quick response. Please see below.

 

[Nige]

Sorry you're out of luck. Some machines have a basic set of gauges as per below. With that setup Diagnostic Codes & Events can be recovered. It is a plug & play into your machine if you can find a company that is dismantling this type of machine. Any of the following Part Numbers - 264-8861, 346-6336, or 363-8111 will work.

 

[Weekend_Warrior]

Sorry you're out of luck. Some machines have a basic set of gauges as per below. With that setup Diagnostic Codes & Events can be recovered. It is a plug & play into your machine if you can find a company that is dismantling this type of machine. Any of the following Part Numbers - 264-8861, 346-6336, or 363-8111 will work.

View attachment 301854

Thank you for the info. Do you have any advice on any other checks I can perform over the long weekend? Do you happen to have the electrical schematics for this machine?

I was thinking about checking the function of solenoids that are linked to the parking brake, but am not sure where to start.

 

[Nige]

Do you happen to have the electrical schematics for this machine?

I do. Keep an eye on your messages. YHM.

 

[Weekend_Warrior]

I do. Keep an eye on your messages. YHM.

Thank you very much, Nige.

 

[Zewnten]

Did you pull on any wiring getting that new hose in there?

 

[Weekend_Warrior]

Did you pull on any wiring getting that new hose in there?

No, I was careful not to disturb anything I wasn't working on.

 

[Weekend_Warrior]

I do. Keep an eye on your messages. YHM.

Thanks for the electrical schematics, Nige. I bought the basic monitor you specified above, part #346-6336, new from Caterpillar.

FYI for folks who are looking to buy one - the parts receptionist said the monitor needed to be flashed to the machine, but one of the lads in the service center said it did not need to be. Only the advanced monitors required flashing.

I found the diagnostics code file you provided from this post: https://www.heavyequipmentforums.com/threads/cat-299c-parking-brake-stuck.93704/

Service mode #1 gave me the following codes:

681-5 (parking brake solenoid low voltage?)
2685-8
2686-8
2687-8
2688-8

Google tells me the 26##-8 codes are related to left and right drive motor speed sensors. I'd like to think that the probability of both the left and right speed sensors being out is very low, and the primary issue is actually related to the brake solenoid. But if the solenoid and drive sensors share a common ground then maybe that's causing all of these codes to come up?

Some additional info - this morning the parking brake disengaged after sitting for a week. I was able to move the machine about 15 yards and then it locked up again. After a few minutes of pressing the switch, it allowed me to move another 10 yards. I then proceeded to disconnecting the battery, installing the monitor above, reconnecting the battery, and then retrieving the codes.

Any idea on what could be causing the 681-5 code? Would a bad solenoid throw the code?

 

[Nige]

Any idea on what could be causing the 681-5 code? Would a bad solenoid throw the code?

681-5 is a Diagnostic Code for the ENTIRE parking brake solenoid circuit, not just the solenoid itself. So it could be something as simple as a wire rubbed through. See where the attached troubleshooting procedure gets you. You will probably need to use it in conjunction with the electrical schematic.

 

[Weekend_Warrior]

681-5 is a Diagnostic Code for the ENTIRE parking brake solenoid circuit, not just the solenoid itself. So it could be something as simple as a wire rubbed through. See where the attached troubleshooting procedure gets you. You will probably need to use it in conjunction with the electrical schematic.

Thank you for the troubleshooting procedure, Nige. I looked through the parts manual and cannot locate the parking brake solenoid. I'm not sure where it is, but some google searches led me to think it's this component circled in red below. Is this accurate?

 

[Nige]

I sent you the electrical schematic. If you look on that you will find tables of components with hyperlinks. Find the solenoid and click on the hyperlink it will take you to the location on the schematic, or on the machine as the case may be, where that part lives.

An alternative would be find the solenoid on the schematic and right next to it you will see the Part Number. Search your Parts Manual for that number - simples…..

 

[Weekend_Warrior]

I sent you the electrical schematic. If you look on that you will find tables of components with hyperlinks. Find the solenoid and click on the hyperlink it will take you to the location on the schematic, or on the machine as the case may be, where that part lives.

An alternative would be find the solenoid on the schematic and right next to it you will see the Part Number. Search your Parts Manual for that number - simples…..

Thanks for the tip. Are there supposed to be more than 4 pages in the file that you sent? Asking because I cannot find any hyperlinks. I see the schematic for the parking brake switch, but not the solenoid. If I am viewing the file incorrectly then please let me know.

 

[Nige]

Sorry, that schematic doesn’t have the tables with the hyperlinks, although the table themselves should exist.

EDIT: Yes they do. Page 1 just to the left of the title. The parking brake solenoid is on Page 2, Grid Location F-12, machine location 36 (look at Page 1 - Engine component locations). The solenoid valve Part Number is 278-8743. You will find it as part of the 258-2405 Hydrostatic Piston Pump.

 

[Weekend_Warrior]

Thanks, Nige.

I found the solenoid and performed the tests from the procedure you sent. Unplugging from the solenoid and jumping the A958-WH(White) to H807-YL(Yellow) wires did not change the diagnostic code from 681-05 to 681-06. This means my solenoid is still good.

Unplugging the J2 connector from the ECM and checking the resistance on those 2 wires yielded much lower than 5.0 ohms. This means the circuit is good.

I didn’t proceed to test #3 since the procedure said it is very unlikely my ECM is bad, and because I don’t have the special tool to remove the wiring.

Thanks for sending the part # for the parking brake solenoid. I think I will replace the solenoid and wish for the best, but before I do I will try cleaning the old one. Maybe some debris may have jammed up the solenoid from when I changed out the hydraulic line?

If you have any other ideas then please advise.

 

[Zewnten]

You unplugged the solenoid and did nothing else, them checked the codes? Next is to short the wires together and re-check the codes. If nothing changed with either condition the sensor shouldn't be your problem.

You checked resistance from wire end to wire end (yellow sensor end to yellow ECM end)? Did you check wire to wire (white to yellow) to make sure they're not shorted together?

Did you preform a tug test on the ends mounted in the connectors to make sure they're not loose?

 

[Nige]

Key question. When you pulled the Codes using the Monitor were the 5 you listed above Active (Service Mode 1) or Logged (Service Mode 2).? If they were Logged the troubleshooting procedure is not likely to find anything, you need the Code to be Active in order to troubleshoot it correctly.

TBH with the problem coming & going as it appears to be my money would be on a wiring harness connector somewhere that has condensation, corrosion, etc, in it, or even a wire rubbed through somewhere.

It might pay you to identify all the major harness connectors between the ECM and the park brake solenoid, open each one up in turn, treat it with electrical contact cleaner then move on to the next one. If there are none then at least clean the ECM connector (J2, Pin 2) and the 2-pin connector at the solenoid end.

 

[Nige]

You checked resistance from wire end to wire end (yellow sensor end to yellow ECM end)? Did you check wire to wire (white to yellow) to make sure they're not shorted together?

I would also suggest to use a test light powered from the battery and grounded to the machine frame. There can be times that a multimeter indicates continuity where only one strand of wire is hanging on by a thread but when subjected to the circuit operating current the wire breaks down.

 

[Nige]

You may find this document useful.