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D6n parking brake won't release

Pushing forward

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Joined
Mar 13, 2023
Messages
48
Location
Missouri
Have a D6N LGP that the parking brake will not release on. Cat technician recommended replacing the main wiring harness as it showed signs of corroding. Replaced it and three solenoids on valves. Still will not releasing. Technician thinks it is internal now. I'm at $12,000.00 dollars repair bill and no closer to getting issue resolved. I took the valves apart and cleaned them thoroughly, making sure the screens were not plugged with debris, made no difference. Has anyone dealt with this issue before? Serial number is ALY02368
 

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Messages
48
Location
Missouri
Currently not by the machine, so can't answer yet. Will be by it in about an hour to find out for sure and can let you know then. Thank you Nige for your quick response.
 

Nige

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Jun 22, 2011
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G..G..G..Granville.........!! Fetch your cloth.
Ok after checking there is one service code but it is not flashing. It is 036. 0091.02
I’m not sure I understand you. When the Codes are displayed on the screen of the Monitor Panel they are not supposed to flash.

When the Code was displayed was the SERV CODE icon to the right of the display window lit or not.?
 

Nige

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Messages
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G..G..G..Granville.........!! Fetch your cloth.
Apart from the fact this is Code is 096F03 and yours is 091F02, does your screen look like this when you are in the diagnostics menu.? (Your screen may be gray rather than orange)

1678742564550.png

It is lit by the sevice code. When the key is cycled it is not lit up by the hours thoug.
Are you saying that when you scroll back to the "main screen" that displays the hourmeter the SERV CODE icon goes off.?
That doesn't make sense because the SERV CODE icon is supposed to be lit any time that there is an Active Diagnostic Code. That's how the operator is supposed to be initially informed that there is an Active Code.
 

Nige

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G..G..G..Granville.........!! Fetch your cloth.
OK, now that makes sense. The panel has to complete the power-up self-test and then go back into normal operating mode before the SERV CODE icon will light up.
091F02 is incorrect throttle switch inputs. Probably nothing to do with your park brake issue but it really needs fixing before you proceed fiurther to avoid muddying the diagnositc waters.

Attached the Troubleshooting procedures. I'll send you an electrical schematic as well. You're probably going to need it.
 

Attachments

  • MID036 CID0091 FMI02.pdf
    146.2 KB · Views: 8
  • Throttle Switch Circuit - Test.pdf
    421 KB · Views: 5

Pushing forward

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Mar 13, 2023
Messages
48
Location
Missouri
Had the all of the panels off to install new harness. Just put the panel with the throttle switch back on and reconnected the switch. Service codes are no longer showing.
 

Nige

Senior Member
Joined
Jun 22, 2011
Messages
28,984
Location
G..G..G..Granville.........!! Fetch your cloth.
OK, moving on...........

Have any pressure tests been performed on the power train and brake system.? Do you have pressure gauges.? Do you know what all the pressure test points are and where they are located.?

I would be extremely interested to see what happens to the pressure at the transmission main relief valve pressure test point when the park brake switch is cycled from ON -> OFF and back again.
 
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