Case IH 3857 – Engine Control Unit (ECU) / EDC (Electronic Diesel Control): Turbine speed errors in PCR - Irreversible Overspeed

The engine's turbocharger turbine has exceeded its maximum allowable safe speed limit (an irreversible overspeed event). This is typically caused by a defective turbine speed sensor giving erratic readings, or a sticking Variable Geometry Turbocharger (VGT) that is failing to regulate boost and turbine speed properly.

• Case IH and New Holland tractors and agricultural equipment equipped with NEF electronically controlled engines

1. 1

   Inspect the turbine speed sensor to ensure it is fixed correctly and not physically loose.

2. 2

   Evaluate the wiring harness for electrical disturbances, damaged signal wires, or an intermittent open circuit on the turbine speed sensor wiring.

3. 3

   Verify the camshaft speed sensor is functioning and its signal is isolated from electrical noise, as unstable signals can interfere with speed evaluation.

4. 4

   Inspect the Electronic Variable Geometry Turbocharger (EVGT) actuator and turbo vanes for mechanical sticking, soot buildup, or binding that would prevent the turbo from governing its own speed.

1. 1

   Harness & Connector Repair

   Disconnect the turbine speed sensor and inspect the pins. Repair any chafed wiring or open circuits in the harness leading back to the EDC. Ensure the harness is properly routed away from high-voltage electrical disturbances.

2. 2

   Sensor Replacement

   If the wiring is intact but the raw speed signal is still erratic or dropping out, remove and replace the defective turbine speed sensor. Ensure it is mounted and torqued correctly.

3. 3

   VGT Actuator Testing

   If the sensor is reading accurately but the turbo is physically overspeeding, actuate the EVGT via a diagnostic tool to check for smooth sweep operation.

4. 4

   Turbocharger Servicing

   If the VGT vanes are sticking, attempt to clean the turbocharger mechanism. If the sticking is severe or the EVGT actuator has failed internally, replace the VGT actuator or the complete turbocharger assembly.

5. 5

   Clear and Verify

   Clear the fault code from the EDC memory. Run the machine under load to verify that the turbine speed remains within normal operating parameters and the code does not return.