Case IH 3821 – Engine Control Unit (ECU / EDC): Throttle Valve Actuator (TVA) Circuit - Short Circuit To Battery (A = 60pin Connector - Engine; A49)

The engine controller has detected that the Out1 circuit (which controls the H-bridge power stage for the Throttle Valve Actuator) is receiving unexpected battery voltage (a short to a 12V source), preventing the ECU from properly commanding this valve.

• skid steer
• Farmall 95U Pro EP
• Farmall 105U Pro EP
• Farmall 115U Pro EP
• Farmall C Series
• Maxxum 135
• Maxxum 145
• Maxxum 150
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)
• SR175

1. 1

   Visually inspect the wiring harness running between the Engine ECU and the Throttle Valve Actuator for chafed, melted, or rubbed-through insulation that could be shorting the signal wire to a 12V power source.

2. 2

   Disconnect the 60-pin connector at the Engine ECU and the connector at the Throttle Valve Actuator to isolate the circuit.

3. 3

   Using a multimeter, test Pin A49 on the ECU's 60-pin engine connector (Out1 TVA) for continuity to battery voltage. If voltage is present while disconnected, there is a short in the wiring harness.

4. 4

   If the wiring harness tests good (no short to battery), test the internal resistance of the Throttle Valve Actuator itself to determine if the solenoid has failed internally and shorted the circuit.

1. 1

   Power Down

   Turn off the machine, remove the key, and disconnect the negative battery terminal to prevent electrical damage.

2. 2

   Access the ECU and TVA

   Locate the Engine ECU (specifically the 60-pin connector) and the Throttle Valve Actuator on the engine intake manifold.

3. 3

   Repair Wiring

   If the diagnostic tests revealed a short in the harness on the Pin A49 circuit, trace the wire, repair the damaged section using proper soldering and heat-shrink tubing, or replace that section of the engine harness.

4. 4

   Replace the TVA

   If the harness is intact but the actuator is internally shorted, unbolt the Throttle Valve Actuator from the intake assembly. Clean the mating surface, install a new gasket/seal, and bolt the new actuator into place. Torque to OEM specifications.

5. 5

   Reassemble and Clear Codes

   Reconnect all harness connectors and the battery. Use a diagnostic scan tool (like the CNH EST) to clear the inactive 3821 fault code.

6. 6

   Test Run

   Start the engine and let it idle. Verify that the engine idle is stable and that the fault code does not return. (Note: If the code immediately returns after verifying the harness and replacing the TVA, the ECU's internal power stage/H-bridge may be permanently damaged and require ECU replacement).