Gen3 - Hardware - Check for Swapped Pressure Sensors

Gen3 - Hardware - Check for Swapped Pressure Sensors

The Gen3-LMS system for telehandlers uses 4 pressure sensors installed into the main lift and compensation cylinders. All 4 pressure sensors are identical and connect into the CPIM module mounted on the chassis. As a result it is easy to accidentally connect the wrong pressure sensors into the wrong ports on the CPIM.
If the pressure sensors are connected into the wrong ports or swapped over between ports the Gen3 system may not read the load at all or may read the load incorrectly only under certain circumstances depending on the pressure sensors that have been swapped and the machine model.
This article will help identify if the pressure sensors have been swapped or connected into the wrong ports.

Identification of the Cylinder Ports

Before explaining how to test the pressure sensor connections we'll first define the naming conventions used to describe the hydraulic cylinder ports

  1. Head Port - The head port is connected into the base of the cylinder. When oil is feed into the head port the cylinder will extend.
  2. Rod Port - The rod port is connected to the rod or piston side of the cylinder. When oil is feed into the rod port the cylinder will retract.
It's possible the hydraulic cylinders may be upside or pointing in different directions depending on the geometric arrangement of the machine. Regardless of the geometry the function of the head and rod ports of the cylinder will remain the same based on the extension/retraction of the cylinder.

Test By Disconnection

The easiest method to determine if the pressure sensor connections into the CPIM are correct is to disconnect the pressure sensor connections and check the corresponding error message in the Gen3.
Before disconnecting the cylinder make sure you fully understand the above Identification of the Cylinder Ports section
  1. N14 Error - Disconnect the head pressure sensor of the main lift cylinder that raises/lowers the boom
  2. N15 Error - Disconnect the rod pressure sensor of the main lift cylinder that raises/lowers the boom
  3. N16 Error - Disconnect the head pressure sensor of the compensation cylinder that keeps the fork attachments level while the boom is raised/lowered
  4. N17 Error - Disconnect the rod pressure sensor of the compensation cylinder that keeps the fork attachments level while the boom is raised/lowered
Disconnect each one of the sensors in turn and note which error messages is shown on the display. Then cross check with the list above to see if it matches your notes. If not then swap the required pressure sensor connections and confirm by repeating the test again.
This test can be performed when the Gen3 system is powered via accessories

Test By Moving Boom

A more reliable method to determine if the pressure sensor connections into the CPIM are correct is to move the boom and check if the pressure sensor readings on the Diagnostics menu behave as expected.
Access the diagnostics menu using the 5 button user control. Press Enter to open the Main Menu and use the arrows to navigate to System Menu -> Diagnostics Menu.
The pressure sensor readings are the first 4 values shown on the diagnostics menu

Follow the steps below to complete the test
  1. Lower the boom so it's resting on the ground
  2. Extend the lift cylinder and raise the boom up to about 25 degrees off the ground. Note the approximate value of the Main Head Pressure and Main Rod Pressure from the Diagnostics Menu.
  3. Retract the lift cylinder and lower the boom by about 5 degrees. Note the approximate value of the Main Head Pressure and Main Rod Pressure from the Diagnostics Menu.
  4. The value of the Main Rod Pressure in step 2 after the lift cylinder has extended should be a low value and in step 3 after the lift cylinder has retracted it should be higher.
    The value of the Main Head Pressure in step 3 after the lift cylinder has retracted should be slightly higher than the value in step 2, due to the higher Main Rod Pressure value.
  5. Slowly extend the tilt cylinder to change the angle of the attachment. While the cylinder is moving note the approximate value of the Compensation Head Pressure and Compensation Rod Pressure from the Diagnostics Menu.
  6. Slowly retract the tilt cylinder to change the angle of the attachment. While the cylinder is moving note the approximate value of the Compensation Head Pressure and Compensation Rod Pressure from the Diagnostics Menu.
  7. The value of the Compensation Head Pressure should be higher than the Compensation Rod Pressure in step 5 when the tilt cylinder is actively extending.
    The value of the Compensation Rod Pressure should be higher than the Compensation Head Pressure in step 6 when the tilt cylinder is actively retracting.

This test relies on the last movement action of the cylinder rather than moving the boom to a set position. For example if the instruction was to raise the boom to 30 degrees and you overshoot to 35 degrees then lower back to 30 degrees it will negate the test results. Instead you should leave the boom at 35 degrees and continue with the test.

The extension/retraction of the tilt cylinder may either tilt up (crowd) or tilt down (dump) the attachment head depending on the geometry of the machine.
For most machines extending the tilt cylinder will tilt up or crowd the attachment head and retracing the cylinder will tilt down or dump the attachment head.
However come machines (such as the JCB 541-70) have the cylinder in the reverse direction and extending the cylinder dumps the attachment and retracting the cylinder crowds the attachment.
The tests are based on the movement direction of the cylinder not the attachment head.

To help diagnose these tests results record a video of the diagnostics screen while completing the test steps and send it through to support@eqss.com.au Make sure to comment when completing each step in the video so our technician can correctly analyse the results.


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