Case IH 3835 – Engine Control Unit (ECU): ECU Power stages: Throttle valve actuator power stage: SRC low.

The Engine Control Unit (ECU) has detected a "Source Low" (SRC low) condition on the power stage circuit that controls the Throttle Valve Actuator (TVA). This indicates that the voltage is too low, which is typically caused by a short circuit to ground in the wiring harness, a failed actuator solenoid (internal short), or a failure within the ECU's internal power stage driver.

• Farmall
• skid steer
• Farmall 95U
• Farmall 105U
• Farmall 115U Pro EP
• Puma
• Steiger
• Maxxum
• Luxxum
• Quantum
• SV250
• SV300
• SR220
• SR250
• TV380

1. 1

   Verify that the battery voltage is sufficient, as low system voltage can disable the power stage diagnosis or cause false flags.

2. 2

   Inspect the wiring harness running between the Engine ECU and the Throttle Valve Actuator for chafed wires, melted insulation, or areas where the harness may be shorting to the engine block/ground.

3. 3

   Disconnect the TVA and ECU connectors and check for water intrusion, corrosion, or bent pins.

4. 4

   Measure the resistance across the pins of the Throttle Valve Actuator to check for an internal short circuit.

1. 1

   Resolve Wiring Issues

   If a short to ground or open circuit is found in the harness during the diagnostic phase, repair the damaged wiring or replace the engine harness section. Clear the codes and retest.

2. 2

   Replace the Throttle Valve Actuator

   If the wiring and connectors test perfectly but the code remains active (or if the TVA fails a resistance test), the actuator itself is internally shorted. Remove the intake ducting, unbolt the faulty Throttle Valve Actuator, and install the replacement unit.

3. 3

   ECU Replacement

   If the fault persists after replacing the TVA and verifying the harness, the ECU's internal H-bridge/power stage driver has likely failed. Replace the Engine Controller (EDC) and use the appropriate Case IH Electronic Service Tool (EST) to reprogram the module and restore self-learning parameters.