Case IH 3664 – ENGINE ECU: EGR command saturation over lower threshold

The Engine Control Unit (ECU) is commanding the Exhaust Gas Recirculation (EGR) valve to close or reach a specific lower position, but the valve is failing to achieve that target. The ECU's command signal has saturated at the lower threshold without receiving the correct position feedback. This is typically caused by a mechanically stuck valve due to soot/carbon buildup, a failing EGR actuator motor, or a sensor mismatch.

• Farmall
• Puma
• Maxxum
• Steiger

1. 1

   Verify system battery voltage, as the ECU may disable power stage diagnostics if voltage is too low or too high.

2. 2

   Inspect the wiring harness and the connector at the EGR valve for chafing, corrosion, or bent pins (look for related circuit codes like 3667 or 3669-3672).

3. 3

   Connect the CNH EST diagnostic tool and monitor the 'Desired EGR Valve Position' versus the 'Actual EGR Valve Position' to see if the valve is stuck or the actuator is dead.

4. 4

   Remove the EGR valve and physically inspect the valve pintle/flap for heavy soot or carbon buildup preventing it from seating.

1. 1

   Preparation

   Turn off the machine, remove the key, and disconnect the negative battery cable to prevent electrical shorts.

2. 2

   Access the EGR Valve

   Locate the EGR valve on the engine (typically mounted between the exhaust manifold and the intake/EGR cooler assembly).

3. 3

   Removal

   Disconnect the electrical harness connector from the EGR valve actuator. Remove the mounting hardware (e.g., M8 x 90mm flange bolts) securing the EGR valve to the manifold/cooler. Carefully remove the EGR valve and discard the old metal gaskets.

4. 4

   Cleaning

   Clean the mating surfaces on the intake and exhaust manifolds. If the old valve is only lightly carbon-fouled, a specialized EGR carbon solvent can sometimes unstick it, but replacement is standard OEM procedure for a failed actuator.

5. 5

   Installation

   Install the new EGR valve using new OEM gaskets. Insert and torque the mounting bolts to the engine manufacturer's specifications. Reconnect the electrical harness connector.

6. 6

   ECU Reset / Calibration

   Reconnect the battery. You must use the CNH Electronic Service Tool (EST) to perform an 'ECU data reset' or 'EGR valve configuration' procedure. This forces the Engine ECU to relearn the new valve's end stops and self-learning parameters.

7. 7

   Verification

   Clear the 3664 fault code and test run the engine under load to ensure the code does not return.