Case IH 3803 – Engine Control Unit (ECU): ECU internal failure - Error on R2S2 module

The R2S2 module is the low-level chip driver for the power-stage chips located inside the engine's computer. This code indicates a fatal internal hardware or software failure within the controller's circuitry that manages high-current outputs (the power stage).

• Farmall
• Farmall series tractors
• SR-series skid steer loaders (e.g., SR175)
• compact wheel loaders (e.g., 21F, 121F, 221F, 321F Tier 4)

1. 1

   Connect the Electronic Service Tool (EST) to confirm that DTC 3803 (2D1-03) is currently active

2. 2

   Inspect the engine wiring harness for any shorts to ground or shorts to power, which can overload the ECU's power-stage chips

3. 3

   Ensure the ECU is receiving clean, stable voltage, as voltage spikes can damage the R2S2 chip driver

1. 1

   Turn off the machine and disconnect the battery ground cable.

2. 2

   Inspect the ECU (A-9000) connectors for water intrusion, bent pins, or corrosion.

3. 3

   Reconnect the battery, turn the key on, and attempt to clear the fault code using the EST.

4. 4

   Cycle the key.

   If the software resets and the code does not return, it may have been a temporary logic glitch.

5. 5

   If the 3803 fault code immediately returns as active, the ECU's internal hardware is permanently damaged.

6. 6

   Remove the defective Engine Control Unit and install a replacement.

7. 7

   Flash the new ECU with the latest machine-specific software using the dealer EST.