Case IH 19755 – DCU: DEF Pump Speed to Dosing Ratio Exceeded

The system monitors the relationship between the DEF pump speed and the DEF dosing valve to ensure the correct amount of fluid is being injected at the correct pressure. When the ratio is exceeded, it means the DEF pump is running at a significantly higher speed than expected for the commanded dosing valve opening. This discrepancy typically indicates the pump is sucking in air, there is a downstream DEF leak, the dosing valve is stuck open, or a clogged DEF filter or line is causing abnormal pump speed deviations.

• Tier 4b
• Magnum 180
• Magnum 200
• Magnum 220
• Magnum 240
• Magnum 250
• Magnum 280
• Magnum 310
• Magnum 340
• Magnum 380
• Maxxum 115
• Maxxum 125
• Maxxum 135
• Maxxum 145
• Maxxum 150
• Puma 140
• Puma 150
• Puma 165
• Puma 185
• Puma 200
• Puma 220
• Puma 240
• Optum
• Steiger
• Axial-Flow 240 series
• Axial-Flow 5130
• Axial-Flow 6130
• Axial-Flow 7130
• Axial-Flow 7240
• Axial-Flow 8240
• Axial-Flow 9240

1. 1

   Inspect the DEF pump wiring and connectors for spread or broken terminals, and check all DEF lines for visible leaks or crystallization

2. 2

   Trace the line from the dosing valve back to the pump, disconnect it from both sides, and blow it out with shop air to ensure there are no blockages or crystallized DEF restricting flow

3. 3

   Unbolt the dosing valve from the exhaust but leave it plugged in, then perform an SCR ADS Self Check via the diagnostic tool to see if the valve is constantly dripping or stuck open

4. 4

   Monitor live data to verify if normal DEF pressure (8.5 to 11 bar) and pump speed (760 to 1000 RPM) are reached, as failure to reach 140 psi despite high RPMs indicates a failing pump or pressure sensor

1. 1

   Clear Blockages

   If the diagnostic checks reveal clogged lines, blow them out with compressed air.

2. 2

   Replace the DEF Filter

   Replace the main 90-micron DEF supply filter, as a clogged filter is a primary cause of pump speed deviations. Case IH recommends replacing this every 3600 hours.

3. 3

   Replace the Dosing Valve

   If the dosing valve was found to be dripping or stuck open during the self-check, disconnect the electrical harness and DEF line, unbolt the valve from the exhaust stream, and install a new dosing valve.

4. 4

   Replace the DEF Pump

   If the lines are clear, the dosing valve is not leaking, and the pump still runs at an excessive speed without building proper pressure (140 psi), the DEF pump module has failed internally and must be replaced.

5. 5

   Re-test

   Reassemble all components, clear the DCU fault codes, and run a manual regeneration or SCR system test to verify the pump speed and dosing ratio have returned to normal parameters.