Case IH 3813 (DTC 235D) - ECU – Engine Control Unit (ECU) / EDC: ECU temperature sensor 1 is too low

The internal temperature sensor chip (LM71) located on the motherboard of the control unit is reporting a temperature value that falls below the minimum allowable physical limit, or the internal SPI communication with this chip has failed.

• MAXXUM T4E
• Case IH 240 Series Axial-Flow Combines (7240, 8240, 9240)
• Case IH tractors, sprayers, and heavy equipment utilizing Tier 3, Tier 4a, and Tier 4b engines equipped with Bosch EDC7 or EDC17 engine controllers

1. 1

   Verify ambient temperature to ensure the machine is not being started in extreme, sub-zero temperatures without a block heater, which could legitimately drive the internal board temperature below the sensor's calibrated threshold.

2. 2

   Check the main battery voltage and the primary power/ground pins at the Engine ECU harness. Low voltage or a poor ground can cause the ECU's internal 5V reference logic to drop.

3. 3

   Check for accompanying codes such as 3814 (SPI Error ECU temperature sensor LM71) or 2461 / 19002 (Battery voltage is lower than expected). If voltage codes are present, fix the power supply issue first.

4. 4

   Clear the inactive faults and cycle the key power. If the fault remains active immediately upon key-on, it is a hard internal hardware failure.

1. 1

   Disconnect battery

   Disconnect the negative battery cable to prevent electrical arcing.

2. 2

   Locate Engine ECU

   Locate the Engine ECU (EDC), typically mounted directly to the side of the engine block on vibration isolators.

3. 3

   Disconnect wiring harnesses

   Carefully release the locking levers on the large 60-pin/94-pin wiring harness connectors and unplug them from the ECU.

4. 4

   Remove faulty ECU

   Remove the mounting bolts securing the ECU to the engine block and remove the faulty unit.

5. 5

   Install new ECU

   Install the new Engine ECU and torque the mounting bolts to OEM spec.

6. 6

   Reconnect wiring harnesses

   Reconnect the wiring harnesses, ensuring the locking levers seat fully.

7. 7

   Reconnect battery

   Reconnect the battery.

8. 8

   Program new ECU

   Use the CNH Electronic Service Tool (EST) laptop to flash the ECU with the correct software payload and engine calibration file matching the machine's serial number.