Case IH F-518-31 - ECU – Engine Control Unit (ECU) / Engine Control Module (ECM): Torque limitation caused by SCR catalyst protection

A protective, consequential fault code indicating that the engine's control system has intentionally limited the engine's torque output (derate) to prevent physical or thermal damage to the Selective Catalytic Reduction (SCR) catalyst. It is triggered when the system detects a severe primary issue within the emissions or aftertreatment system.

• MAGNUM AFS Connect
• 240 Series Axial-Flow Combines (7240, 8240, 9240)
• Magnum series
• Steiger series
• Farmall series (115U)
• Case N-Series Loader Backhoes

1. 1

   Scan for primary fault codes using the Case IH Electronic Service Tool (EST) to identify issues with NOx sensors, EGT sensors, DEF dosing pressure, or DEF quality.

2. 2

   Test DEF quality by extracting a sample from the tank and testing it with a refractometer (must be exactly 32.5% urea concentration).

3. 3

   Inspect the DEF dosing system, checking the DEF injector (dosing valve) for crystallization or blockages, and ensuring lines are not pinched, leaking, or frozen.

4. 4

   Check exhaust sensors by monitoring live data for upstream and downstream NOx sensors and EGT sensors to ensure plausible values and no shorts.

1. 1

   Address the Primary Failure

   Repair or replace the component identified by the primary fault codes (e.g., drain and refill contaminated DEF, replace a failed NOx sensor, or clean a clogged DEF dosing valve).

2. 2

   Prime the DEF System

   If the DEF lines or dosing valve were opened or replaced, run a DEF system prime command via the EST to evacuate air from the lines.

3. 3

   Perform a Stationary Regeneration / SCR Test

   Once the physical repair is complete, use the EST to initiate an SCR System System Test or a forced stationary DPF/SCR regeneration. This allows the ECU to verify that the emissions system is functioning correctly and that NOx reduction is back within the legal threshold.

4. 4

   Clear Codes

   Once the test completes successfully, the ECU will change the F-518-31 code from 'Active' to 'Inactive.' Clear the inactive codes from the ECU memory.

5. 5

   Test Drive

   Operate the machine under load to verify that full engine torque has been restored and no warning lights return.