New Holland 3405 – ECU: ECU Power Stages: Open Load Temperature Error on Turbocharger PWM Output Power Stage

The Engine Control Unit (ECU) has detected an open load or open circuit condition on the Pulse Width Modulated (PWM) output power stage that controls the turbocharger's wastegate actuator. This indicates that the ECU is sending a control signal but is not detecting the expected electrical load in return, which points to a broken circuit, a failed actuator coil, or an internal ECU driver fault. It may also be triggered by an over-temperature condition in the ECU's power stage driver circuit.

• T5.95
• T5.105
• T5.115
• T6.120
• T6.125
• T6.140
• T6.145
• T6.155
• T6.160
• T6.165
• T6.175
• T6.180
• T7.165
• T7.175
• T7.185
• T7.190
• T7.210
• T7.220
• T7.225
• T7.230
• T7.245
• T7.250
• T7.260
• T7.270
• T6030
• T6050
• T6070
• T6080
• T6090
• T7030
• T7040
• T7050
• T7060
• T7070

1. 1

   Verify the fault is active using an Electronic Service Tool

2. 2

   Inspect the wiring harness and connectors between the ECU and the wastegate valve for damage or corrosion

3. 3

   Test the electric turbocharger wastegate valve for internal open circuits

4. 4

   Check the signal wire continuity between the ECU and the wastegate valve

5. 5

   Verify the 12V power supply to the wastegate valve

6. 6

   Evaluate the ECU for an internal power stage failure

1. 1

   Inspect wiring and connectors

   Turn the key switch OFF. Visually inspect the ECU connector (X-939) and the electric wastegate valve connector (X-960). Check for secure connections, corrosion, or physical damage. Inspect the wiring harness between the ECU and the wastegate valve for any signs of damage, corrosion, or improper routing. Repair or replace affected harness or connectors if damage is found. After repair, clear the faults and re-test to confirm the issue is resolved.

2. 2

   Test electric wastegate valve

   With the key switch OFF, disconnect the wastegate valve connector (X-960). Measure resistance across pins 1 and 2 of the valve. Expected result is less than 100 Ω. If greater than 100 Ω, the valve has an open circuit and should be temporarily replaced with a known good part to confirm the diagnosis.

3. 3

   Test signal wire continuity

   With the key switch OFF and both connectors (X-939 and X-960) disconnected, measure resistance between pin 2 of the valve harness connector and pin 4 of the ECU harness connector. Expected result is less than 10 Ω. If greater than 10 Ω, repair or replace the damaged signal wire.

4. 4

   Test power supply to valve

   Reconnect the ECU connector but leave the wastegate valve disconnected. Turn the key switch ON. Measure voltage from pin 1 of the valve harness connector to a known good chassis ground. Expected result is approximately 12V. Wiggle the harness to check for intermittent connections. If 12V is not present, further diagnosis of the power supply from the ECU is required.

5. 5

   Check ECU

   If all wiring, power supply, and the wastegate valve test within specification, the fault likely lies within the ECU's internal power stage. Temporarily replace the ECU with a known good unit to see if the fault is eliminated.