Case IH 3813 – Engine Control Unit (ECU) / Electronic Diesel Control (EDC): Physical Range Check low for ECU temperature sensor

The internal temperature sensor (specifically the LM71 sensor chip) located inside the Engine Control Unit (ECU) is reporting a temperature value that falls below the minimum plausible physical limit, indicating an erratic, out-of-bounds, or failing internal sensor reading.

• Farmall
• Steiger T4B
• FPT engines (F5C, F5H, NEF)
• Tier 3 and Tier 4a
• Case IH skid steer loaders (e.g., SR175)
• compact track loaders
• tractors

1. 1

   Connect the CNH Electronic Service Tool (EST) to the machine's diagnostic port

2. 2

   Turn the ignition to 'Key On, Engine Off' and verify if fault code 3813 is currently active or stored

3. 3

   Check for any other related internal ECU codes (such as 3814 - SPI Error ECU temperature sensor LM71)

4. 4

   Check for available software updates, as erratic internal voltage or sensor logic can sometimes be resolved by updating the module's software

1. 1

   Attempt Software Re-initialization

   Using the EST service tool, attempt to re-initialize the ECU and load the appropriate data-set for the specific engine type. (Note: This step typically requires a dealer to call CNH Technical Support (TSS) to get an authorization code for the ECU initialization download).

2. 2

   Clear and Retest

   Clear the fault codes using the EST. Cycle the key off, then back to 'Key On, Engine Off' and check if the fault code returns.

3. 3

   Replace the ECU

   If the fault code does not clear or immediately returns after the software re-initialization, the internal LM71 sensor has permanently failed. The sensor cannot be serviced independently. You must remove and replace the entire Engine Control Unit (ECU).

4. 4

   Program the New ECU

   Install the replacement ECU and use the EST to flash the module with the correct data-set for your specific machine and engine configuration.