Case IH 19072 – Engine Control Unit (ECU): SCR catalyst efficiency lower than second NOx production threshold level

The Selective Catalytic Reduction (SCR) system is failing to reduce Nitrogen Oxides (NOx) emissions efficiently enough to meet the secondary regulatory threshold. The system determines this by comparing the NOx levels measured by the upstream NOx sensor to the downstream NOx sensor.

• Tier 4b
• Case IH Magnum
• Case IH Steiger
• Case IH Quadtrac
• Case IH Puma
• Case IH Maxxum
• Case 650M
• Case 850M
• Case 1650M
• Case 580N
• Case 590SN

1. 1

   Check for leading active faults (such as DEF pressure faults, DEF quality faults, or NOx sensor plausibility errors)

2. 2

   Check DEF (Diesel Exhaust Fluid) quality to ensure it is ISO 22241-compliant (32.5% urea concentration) and not degraded or contaminated

3. 3

   Inspect the DEF dosing system (supply pump, DEF filter, and dosing injector) for blockages, crystallization, or failure

4. 4

   Verify NOx sensor accuracy using an Electronic Service Tool (EST) for both upstream and downstream sensors

5. 5

   Inspect the exhaust system for leaks between the engine and the SCR catalyst, and ensure piping and decomposition tube are mounted correctly and undamaged

6. 6

   Inspect the SCR catalyst face for physical damage, soot plugging, or heavy DEF crystallization

1. 1

   Address Leading Faults

   Correct any other active fault codes related to the DEF dosing system or NOx sensors first.

2. 2

   Service the DEF System

   If DEF quality is poor, drain the tank, flush the system, and refill with fresh DEF. Replace the DEF supply filter. Clean or replace the DEF dosing injector if it is clogged with crystallized urea.

3. 3

   Replace Faulty Sensors

   If EST diagnostics prove a NOx sensor is reading inaccurately, replace the affected sensor.

4. 4

   Replace the SCR Catalyst

   If the DEF system is dosing correctly, the sensors are accurate, there are no exhaust leaks, and the code persists, the SCR catalyst has deteriorated and must be replaced.

5. 5

   Perform the Verification Drive Cycle

   After the repair is completed, the engine must be brought up to operating temperature and run under load until the ECU can verify that the SCR system is operating properly and NOx reduction is back within the acceptable threshold to clear the fault code.