Case IH 3827 – Engine Control Unit (ECU): Throttle Valve Actuator (TVA) Circuit - Under Voltage Error For H-Bridge

The Throttle Valve Actuator (TVA) is driven by an H-bridge circuit. Code 3827 indicates that the voltage supplied to this H-bridge circuit has dropped below the minimum acceptable threshold. This is usually caused by a failing battery/alternator, a wiring issue causing a voltage drop, or an internal failure of the ECU's power stage.

• Farmall
• skid steer
• Farmall 95U
• Farmall 105U
• Farmall 115U Pro EP
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)
• SV300
• Steiger
• Puma

1. 1

   Verify the overall electrical system by checking the battery resting voltage and the alternator output while running to ensure there are no severe voltage drops or high voltage fluctuations.

2. 2

   Inspect the wiring harness between the Engine ECU and the Throttle Valve Actuator for chafed wires, corrosion, or loose pins at the connectors.

3. 3

   Test the specific power supply and ground circuits feeding the ECU and the TVA to ensure they are receiving full battery voltage under load.

1. 1

   Resolve Supply Issues

   If the diagnostic checks reveal a weak battery, failing alternator, or damaged wiring harness, repair or replace the affected electrical components first. Clear the code and cycle the key to see if the fault returns.

2. 2

   Replace the TVA

   If the vehicle's voltage is stable and the wiring to the actuator is intact, the internal circuitry or solenoid of the Throttle Valve Actuator has likely failed and is pulling the voltage down. Replace the Throttle Valve Actuator.

3. 3

   Replace the ECU

   If the fault persists after replacing the TVA and verifying the wiring, the H-bridge power stage inside the Engine Controller (ECU) has failed (often due to high voltage fluctuations in the system). The ECU will need to be replaced.

4. 4

   Restore Parameters

   If either the ECU or the TVA is replaced, use the appropriate Case IH Electronic Service Tool (EST) procedure to restore self-learning parameters and calibrate the new valve.