Case IH 3668 – Engine Control Module (ECM / EDC): EGR Over Temperature Error for H-bridge

The H-bridge circuit is overheating because the EGR valve motor is drawing excessive electrical current. This is almost always caused by a mechanically stuck or binding EGR valve, an internal electrical short within the EGR valve motor, or a short circuit in the wiring harness.

• Farmall
• SR175
• SR240B
• SV280B
• TR320
• L220
• L230
• C238
• 115U
• Maxxum
• Puma
• 580N
• 570N
• 586H

1. 1

   Mechanical Inspection: Remove the EGR valve and inspect it for severe carbon or soot blockage. Try to actuate the valve manually to see if it is physically jammed (addresses mechanically stuck or binding EGR valve).

2. 2

   Electrical Testing: Test the resistance of the EGR valve motor pins with a multimeter to check for an internal short circuit (addresses internal electrical short within the EGR valve motor).

3. 3

   Inspect the wiring harness between the Engine ECM and the EGR valve for chafing, melted insulation, or shorts to ground/battery, specifically on pins A50 and A35 (addresses short circuit in the wiring harness).

4. 4

   Check battery and system voltage to ensure low voltage is not causing the EGR motor to draw higher amperage.

1. 1

   Disconnect Power

   Turn off the battery quick-disconnect switch (if equipped) or disconnect the negative battery cable to prevent electrical spikes.

2. 2

   Access the EGR Valve

   Locate the EGR valve on the engine block (situated between the exhaust manifold and intake routing).

3. 3

   Disconnect Wiring

   Unplug the electrical connector from the EGR valve. Inspect the connector pins for corrosion or heat damage.

4. 4

   Remove the Valve

   Remove the mounting bolts securing the EGR valve to the engine. Carefully remove the valve and discard the old metal gasket.

5. 5

   Clean Passages

   Inspect the mating surfaces and the EGR cooler/intake passages. Use a shop vacuum and appropriate solvent to clean out loose soot or carbon buildup so the new valve doesn't immediately ingest debris.

6. 6

   Install New Parts

   Install the replacement EGR valve using a new gasket. Torque the mounting bolts to the specifications outlined in your specific machine's service manual.

7. 7

   Reassemble and Calibrate

   Reconnect the electrical harness and battery. Connect a diagnostic scan tool (like the CNH Electronic Service Tool) to clear the inactive 3668 fault code. Run the engine up to operating temperature to ensure the code does not return and the engine speed is no longer derated.