Case IH 3814 – Engine ECU: ECU temperature sensor: SPI Error ECU temperature sensor (LM71)

The LM71 is a temperature-sensing microchip located internally on the circuit board of the engine controller. An "SPI Error" (Serial Peripheral Interface error) means that the main processor inside the controller has lost communication with this internal temperature sensor. This indicates an internal hardware failure within the module itself.

• Farmall
• Steiger T4B
• Magnum
• Steiger
• Maxxum
• Puma
• Axial-Flow 240 Series
• 7240
• 8240
• 9240
• SR160
• SR175
• SV185
• TR series
• Case wheel loaders
• crawler dozers
• backhoes

1. 1

   Cycle the key power to check if the fault is active or inactive, as a temporary voltage spike can cause a momentary internal communication glitch.

2. 2

   Check power and ground to verify that the Engine ECU is receiving clean, stable power from the battery and alternator. Poor grounding can cause internal ECU logic errors.

3. 3

   Connect the Case IH Electronic Service Tool (EST) and check for software updates. In some Bosch EDC systems, false internal codes can be resolved by updating the software payload.

1. 1

   Disconnect battery

   Disconnect the machine's battery (negative terminal first) to prevent electrical arcing.

2. 2

   Locate Engine ECU

   Locate the Engine ECU (typically mounted directly to the side of the engine block or in a dedicated electronics bay).

3. 3

   Disconnect wiring harness

   Carefully unlock and disconnect the main wiring harness connectors from the ECU.

4. 4

   Remove defective ECU

   Unbolt the defective ECU from its mounting bracket and remove it.

5. 5

   Install replacement ECU

   Install the replacement ECU and secure the mounting hardware.

6. 6

   Reconnect wiring harnesses

   Reconnect the wiring harnesses, ensuring the connector locks are fully seated.

7. 7

   Reconnect battery

   Reconnect the battery.

8. 8

   Program new ECU

   The new ECU will be blank or contain generic software. You must use the Case IH Electronic Service Tool (EST) to flash the correct software payload (dataset) for the specific machine's VIN/Serial Number.

9. 9

   Perform post-installation routines

   Perform any necessary post-installation routines, such as injector coding or throttle position relearns, as prompted by the EST software.