Case IH 3352 – Engine Control Unit (ECU) / EDC (Electronic Diesel Control): Engine compression brake low side driver circuit short to battery failure

The Engine Control Unit has detected that the ground-side (low side) circuit controlling the engine compression brake relay or decompression valve is receiving unintended battery voltage, indicating a short circuit.

• Steiger T4B
• Case IH 240 Series Axial-Flow Combines
• Case IH Magnum 235-340 Tractors
• Case IH Steiger Tractors

1. 1

   Check the Engine Brake Relay (Main Relay 4) for internal short circuits

2. 2

   Inspect the wiring harness from the Engine ECU to the engine brake relay and decompression valve actuator for chafed, melted, or pinched wires

3. 3

   Verify that no external power sources or aftermarket accessories are tapped into the engine brake circuit, causing a voltage backfeed

1. 1

   Power Down

   Turn off the machine and disconnect the battery to prevent electrical spikes during testing.

2. 2

   Locate Components

   Find the Engine ECU, the engine brake relay (Main Relay 4), and the decompression valve actuator on the engine.

3. 3

   Test the Relay

   Remove the engine brake relay and test it with a multimeter. If the relay is internally shorted, replace it.

4. 4

   Harness Continuity and Short Test

   With the relay removed and the ECU disconnected, use a multimeter to test the low-side driver circuit wire for continuity to battery power.

5. 5

   Repair Wiring

   If a short to battery voltage is found in the harness, locate the damaged section of the wire and repair or replace the harness.

6. 6

   Reassemble and Clear Codes

   Reconnect the ECU, install a new or tested relay, reconnect the battery, and use a diagnostic tool to clear the fault code. Test the engine compression brake to ensure the code does not return.