Case IH 3933 – Engine Control Unit (ECU) / Electronic Diesel Control (EDC): Info: SCR Inducement: Warning Block 6 activated

This is an emissions-related inducement code indicating the engine control system has detected a critical failure in the Selective Catalytic Reduction (SCR) system. Because the machine can no longer properly reduce NOx emissions, the computer activates a programmed safety feature ('Warning Block 6') that intentionally derates the engine's power or limits vehicle speed (limp mode) to force the operator to repair the emissions system.

• Magnum Series Tractors (225, 235)
• Steiger Series Tractors (450)
• Puma Series Tractors (160, 185)
• Maxxum Series Tractors (140)
• Axial-Flow Combines (9230)

1. 1

   Scan for primary codes using the CNH Electronic Service Tool (EST) to find the root code (e.g., EGT sensor variance, NOx sensor failure, or DEF pump pressure faults)

2. 2

   Verify DEF (AdBlue) quality in the tank, checking for old fluid, water contamination, or crystallization

3. 3

   Inspect wiring harnesses near the exhaust and heat shields for cracked insulation, vibration fatigue, or rubbing that causes open circuits

4. 4

   Test the DEF dosing injector for mechanical blockages or a collapsed spray pattern

5. 5

   Check Exhaust Gas Temperature (EGT) sensors for an implausible temperature difference reading

6. 6

   Pressure-test the DEF pump to check for seal wear, overheating, or crystallized residue inside the pump

1. 1

   Address the Root Cause

   Based on your diagnostic checks, perform the necessary physical repair. This may involve draining and flushing the DEF tank, replacing a burnt NOx/EGT sensor, or replacing a clogged DEF dosing injector.

2. 2

   Do Not Disconnect the Battery

   Disconnecting the battery will not reset an SCR inducement code. The fault will return immediately once the system runs its self-check.

3. 3

   Reset the SCR System via EST

   Connect the CNH EST laptop. You must use the software to clear the fault codes and reset the SCR system out of limp mode.

4. 4

   Perform a Parked Regeneration / SCR Efficiency Test

   The system must validate the repair. Run a parked regeneration. The engine will need to run under load or at high exhaust temperatures (often over 425°F) for a specific duration (e.g., 30+ minutes) to burn out residue and allow the system to 'heal'.

5. 5

   Monitor LARMF Compensation

   During the SCR efficiency test, monitor the LARMF compensation value on your diagnostic tool. The number must read 0.91 or higher to pass.