Case IH 3403 – Engine Controller (EDC / ECU): Engine Controller Starter Relay Circuit Low Side Driver / HS Power Stage Overtemperature

The Engine Control Unit (ECU) has detected an over-temperature condition on the internal driver (power stage) that controls the starter relay. This is triggered when there is excessive current draw or a short circuit (to ground or battery) in the starter relay circuit, causing the ECU's internal components to overheat.

• Farmall
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)
• Puma
• Steiger
• Maxxum
• CX series
• JX series
• Axial-Flow 7230
• Axial-Flow 8230
• Axial-Flow 9230

1. 1

   Test the starter relay coil for internal shorts or excessive resistance that could pull too much current from the ECU

2. 2

   Inspect the wiring harness between the Engine Controller (ECU) and the starter relay for chafed wires causing a short to ground or battery

3. 3

   Measure the current draw on the starter relay control circuit to ensure it is within the ECU's safe operating limits

4. 4

   Ensure all ground and battery connections to the ECU and starter circuit are clean and tight

1. 1

   Disconnect Power

   Always disconnect the battery before servicing ECU-controlled electrical circuits.

2. 2

   Replace the Relay

   If the starter relay fails testing (or as a preliminary inexpensive step), replace the starter relay with a genuine OEM replacement.

3. 3

   Repair Wiring

   If a short is found in the harness between the ECU and the relay, repair or replace the affected wiring section.

4. 4

   Clear Codes and Retest

   Reconnect the battery, clear the fault codes using a diagnostic service tool, and attempt to start the machine.

5. 5

   ECU Replacement (Worst-Case)

   If the failure persists after a short time and all wiring/relays are confirmed to be in good working order, the internal power stage of the Engine Controller is permanently damaged. In this case, you must replace the EDC/ECU.