Case IH U16 – MRM: Rod accumulator pre-charge pressure problem

The fault indicates a Rod accumulator pre-charge pressure problem. Hydraulic accumulators use a pressurized nitrogen gas pre-charge to absorb shocks and maintain system pressure. This code triggers when the system detects that the pressure in the rod-side accumulator has fallen outside of the specified operating range. This can be caused by a physical loss of nitrogen gas (a flat or leaky accumulator), a faulty pressure switch giving a false reading, or a damaged wiring harness interrupting the signal from the switch to the module.

• Magnum 180
• Magnum 200
• Magnum 220
• Magnum 240
• Magnum 340
• Puma

1. 1

   Check the wiring harness leading to the accumulator pressure switch for chafing, breaks, or corrosion. Verify continuity and ensure there are no shorts to ground.

2. 2

   Test the pressure switch to ensure it is opening/closing at the correct pressure thresholds.

3. 3

   Manual Pre-charge Check: If the electrical circuit is intact, the accumulators may be leaky or flat. Perform a manual check on the nitrogen pre-charge using an accumulator charging kit and gauge to see if it meets OEM specifications.

1. 1

   Depressurize the System

   Ensure the tractor is turned off, the implement/suspension is fully lowered, and all hydraulic pressure is relieved from the circuit before servicing.

2. 2

   Harness/Switch Replacement

   If the diagnostic checks reveal a faulty pressure switch or damaged wiring, replace the switch or repair the harness connector.

3. 3

   Adjust Pre-charge

   If the manual pressure check shows the accumulator is flat but holding a charge, use a nitrogen charging kit to adjust the pre-charge pressure back to the factory specification.

4. 4

   Replace Accumulator

   If the accumulator is leaking nitrogen internally (bladder/piston failure) or externally, it cannot be repaired and must be replaced.

5. 5

   Reassemble and Test

   Install the new accumulator or switch, replace any disturbed O-rings, and run the tractor's active suspension/hydraulic calibration procedure to clear the MRM fault code.