Case IH 3546 – Engine Controller (EDC / Engine ECU): Info: SCR Dosing Valve Overheat Protection - Torque Limitation Level1 for SCR Protection active

The Engine Control Unit (ECU) has received a CAN message from the Dosing Control Unit (DCU) indicating that the SCR dosing valve (also known as the DEF injector) is not being cooled sufficiently. To protect the dosing valve from catastrophic heat damage, the ECU actively limits the engine's torque output (Level 1 derate). The dosing valve relies on the continuous flow of Diesel Exhaust Fluid (DEF) to keep it cool during operation.

• Case IH Magnum series (235 - 340, Series 4)
• Case IH Steiger series
• Case IH Puma series

1. 1

   Inspect the DEF supply and return lines running from the DEF pump to the SCR dosing valve for kinks, pinches, leaks, or blockages

2. 2

   Verify that the exhaust heat shields and insulation blankets surrounding the SCR dosing valve and exhaust pipe are intact and properly mounted

3. 3

   Inspect the main paper element DEF filter and the internal strainers located inside the DEF supply module housing for clogs

4. 4

   Check for related codes such as 3555 (CAN Message timeout SCR2 from DCU) or DEF pressure codes, which might indicate a failed DEF pump rather than a failed injector

1. 1

   Cool Down

   Turn off the engine and allow the exhaust system and SCR catalyst to cool completely to avoid severe burns.

2. 2

   Access the Valve

   Locate the SCR dosing valve on the exhaust pipe. Remove the bolts securing the exhaust shield bracket and set the bracket aside.

3. 3

   Remove Insulation

   Open or remove the insulation blanket surrounding the exhaust pipe and dosing valve area.

4. 4

   Disconnect Lines

   Carefully disconnect the electrical harness connector from the dosing valve. Disconnect the DEF supply hose (be prepared to catch a small amount of spilled DEF).

5. 5

   Remove the Valve

   Remove the support clamp bolts or V-band clamp securing the dosing valve to the exhaust pipe. Pull the dosing valve out of its mounting boss.

6. 6

   Install New Valve

   Clean the mounting boss on the exhaust pipe. Insert the new SCR dosing valve and secure it with the clamp/bolts. Torque to OEM specifications.

7. 7

   Reconnect

   Reconnect the DEF supply line and the electrical harness connector.

8. 8

   Reassemble

   Reinstall the insulation blanket and the exhaust heat shield bracket.

9. 9

   Clear Codes & Test

   Connect the Electronic Service Tool (EST), clear the fault codes, and cycle the key. Run the machine or perform a stationary regeneration to verify that DEF is dosing correctly and the overheat code does not return.