Case IH 3834 – Engine Control Unit (ECU): ECU Power stages: Throttle valve actuator power stage: SRC High

The Engine Control Unit (ECU) has detected a "Source High" (SRC High) condition in the H-bridge power stage circuit that controls the Throttle Valve Actuator (TVA). This typically indicates that the voltage on the circuit is higher than expected, which is usually caused by a short circuit to the battery/power source or an open load/circuit in the wiring.

• Farmall
• skid steer
• Farmall 95U
• Farmall 105U
• Farmall 115U Pro EP
• Steiger
• SV300
• 21F
• 121F
• 221F
• 321F
• 580N
• 580SN
• 590SN

1. 1

   Inspect the wiring harness and connectors between the Engine ECU (60-pin engine connector) and the Throttle Valve Actuator for physical damage, corrosion, or loose pins

2. 2

   Measure the resistance of the harness circuit (should be less than 10 ohms)

3. 3

   Physically wiggle the harness while measuring resistance to reveal any intermittent open or short conditions

4. 4

   Test the TVA pins (e.g., Pins A34 and A49 on the ECU connector) for a short circuit to the battery

1. 1

   Disconnect Power

   Disconnect the machine's battery to ensure safety before working on the electrical system.

2. 2

   Isolate the Circuit

   Disconnect the wiring harness from both the Throttle Valve Actuator (TVA) and the Engine ECU.

3. 3

   Test and Repair Wiring

   Perform the resistance and wiggle tests mentioned above. If the harness fails the test (resistance > 10 ohms or a short to power is detected), repair the damaged wiring or replace the engine wiring harness. Re-test to confirm the elimination of the fault.

4. 4

   Inspect the Actuator

   If the harness tests OK, the fault may lie in the Throttle Valve Actuator itself. Check the actuator for internal shorts. Replace the TVA if it is faulty.

5. 5

   Replace the ECU

   If both the harness and the TVA are functioning correctly and the fault persists, the service manual indicates that the fault lies within the ECU's internal power stage. You will need to replace the Engine Control Unit (ECU).

6. 6

   Finalize

   Reconnect all components, reconnect the battery, clear the fault codes using a diagnostic service tool, and cycle the key to verify the repair.