Pc360-11 auxiliary pressure relief

[warpspeed]

Pc360-11 setup for hammer, switched return line to auxiliary valve, hooked up grapple bucket, it works but getting pump relief codes.


Current Abnormality
KOMATSU
09625.6m
! L03 DHZCL8 System Abnormality
L03 DHZAMA System Abnormality
L03 DWPUKA Hydraulic System Abnormality
L03 DXEKKA Hydraulic System Abnormality

Any help is appreciated, and contacts of independent KOMATSU mechanics near dayton ohio.

 

[nikthewho]

Those codes point to the PC360’s electronic pump‑control and main hydraulic control seeing an abnormal load/pressure condition, which is very often what happens when a hammer/aux circuit is plumbed in a way that forces oil over main relief instead of to T‑line while running a grapple or other continuous‑flow attachment.

The grapple return is probably tied into an auxiliary work port or a restricted return instead of a true low‑pressure return to tank, so when you close the grapple and stall it, the pump destroke logic sees continuous high pressure and throws those L03 hydraulic system abnormality codes. PC360 hammer mode expects: P‑line from hammer/aux spool, and R‑line into a dedicated return‑to‑tank or direct return manifold, not into another valve section, case drain, or small port on the spool stack.

 

[warpspeed]

Thank you,


The "return line" is tied into the second port of the auxiliary valve on the manifold instead of return to tank as before. This grapple is a 2 way hydraulic cylinder.

I switched the display "work mode" to 2 way, and adjusted the pressures thru the display to 3500 psi which is the grapples max.

If the grapple was plumbed into a low pressure return, the cylinder would only go one way.....

I did not add or change any relief valve, assumed that was built in the auxiliary valve. What else might need changed?

Thank you for your help

 

[nikthewho]

With a 2‑way cylinder grapple, both hoses must go through the auxiliary work ports (P and A/B) and neither hose should be on a true low‑pressure “hammer‑style” return‑to‑tank; that part of your logic is right, but the current setup is probably keeping the PC360’s pump control at or near main relief when you stall the grapple, which is why the L03 hydraulic abnormality codes are still appearing.

How the 2‑way setup should work​

For a double‑acting cylinder attachment on a PC360‑11 with programmable auxiliary modes:

• Both grapple ports should be on the 2‑way auxiliary work ports (often marked AUX1 P and AUX1 A/B on the boom/stick or manifold), so that when you stroke the joystick one way, port A is pressure and port B is return, and vice versa when you stroke the other way.
• The display must be set to a 2‑way attachment mode (ATT/E 2‑way or similar) with the correct flow and pressure limit (you already set 3500 psi, which matches the grapple’s rating), so the controller knows it is driving a bidirectional cylinder and it will alternate which work port is “pressure” and which is “return” depending on joystick direction.
• In this arrangement, the “return” from the cylinder at any moment is just the opposite work port; it is not supposed to go to a dedicated low‑pressure tank port as with a one‑way hammer circuit.

Why you still see pump relief / L03 codes​

Even with work mode on 2‑way and pressure limited to 3500 psi, a few things can still make the pump protection logic unhappy:

• If the auxiliary valve section is configured internally for single‑acting (hammer) on that second port (for example, check valves or orifices fitted for one‑way flow), oil trying to return through that port when you reverse the cylinder can see very high back‑pressure, so the pump thinks it is at or above main relief for too long and throws hydraulic system abnormality codes.
• If the machine was originally ordered with a “breaker plus return‑to‑tank” kit and later upgraded to true 2‑way auxiliary, there may be optional cartridges or plugs that should be changed to convert that second port from a dump‑to‑tank path into a full function work port with proper cross‑port relief / load‑holding; without that hardware change, the electronic settings in the monitor alone cannot fix the hydraulic behavior.
• On machines with programmable attachment modes, if the attachment circuit selected in the monitor does not match the physical plumbing (e.g., display is set for AUX2 while hoses are on AUX1), the ECM may not modulate the correct solenoids and reliefs, and it can see abnormal pump pressure patterns.komatsu

What likely needs to be changed (beyond display settings)​

Given what you described, the “what else” is probably in the iron, not in the monitor:

• Confirm which auxiliary circuit your hoses are actually on (AUX1 vs AUX2, and which pair of ports on the manifold), then in the monitor assign “2‑way cylinder / grapple” mode specifically to that circuit number so the correct solenoids and pressure limits are used.
• Have someone pull the auxiliary valve section parts list / installation sheet for your PC360‑11 serial number; Komatsu’s double‑auxiliary option uses different internal plugs, check valves and sometimes separate cross‑port relief cartridges for 2‑way versus hammer / single‑acting configurations, and the manual will specify which parts must be installed or removed when converting that second port from return‑to‑tank duty into a full 2‑way work port.
• If the auxiliary valve section currently relies only on the machine’s main relief and does not have its own cross‑port relief or cushion valves on that second port, fitting the proper relief / anti‑shock cartridges for a 2‑way circuit will both protect the grapple and prevent the main pumps from having to go straight to main relief every time you dead‑head the cylinder at 3500 psi.

Practical steps you can take​

Without changing hose routing again, these are practical actions:

• Verify in the monitor that:
  • The correct AUX circuit is selected.
  • It is set to “2‑way”.
  • Pressure limit is at or below 3500 psi.
  • Flow is not maxed out unnecessarily (excess flow just keeps the pump at high load when you stall the grapple).
• With someone in the cab and you watching, gently stall the grapple in both directions and listen/feel: if you get a hard, continuous relief squeal and the engine lugging heavily for more than a second or two, the auxiliary section likely lacks proper cross‑port relief or has internal checks/orifices arranged for single‑acting, and hardware changes on that valve section are needed.
• At that point, involving a Komatsu‑trained tech (dealer or experienced independent) to look up the exact valve configuration for the machine’s serial and confirm the correct cartridges/plugs for a 2‑way cylinder attachment is the most efficient way to eliminate the L03 pump/hydraulic abnormality codes without guessing.

 

[warpspeed]

thank you. I unplugged the auxiliary coil and codes went away, plugged it back in and they are still gone. Hopefully it is fixed. I will share that this is a https://hkx.com/ kit and if you enter your kit number, they have installation instructions and tech support.