Case IH 3802 – Engine ECU (EDC): Turbine upstream pressure sensor: SRC low for Turbine upstream pressure sensor

The signal voltage from the turbine upstream pressure sensor (exhaust back pressure sensor) is excessively low (Source Low), indicating an electrical issue such as a short circuit to ground, an open circuit, a failed sensor, or a physical issue like a severe exhaust leak or soot-blocked sensor tube.

• Farmall
• skid steer
• tractors
• combines
• wheel loaders

1. 1

   Visually inspect the wiring harness and connectors leading to the turbine upstream pressure sensor for damaged wires, chafing, or a short circuit to ground

2. 2

   Disconnect the sensor and check for bent, corroded, or dislocated pins on both the sensor side and the harness side

3. 3

   Check the exhaust manifold and piping upstream of the turbocharger for severe exhaust leaks, which can cause a genuine low-pressure reading

4. 4

   Remove the sensor and check the mounting port/tube for heavy soot or carbon buildup that might be blocking the sensor from reading the exhaust pressure accurately

1. 1

   Turn the ignition OFF and allow the engine and exhaust system to cool completely.

2. 2

   Locate the turbine upstream pressure sensor.

   It is typically mounted on or near the exhaust manifold before the turbocharger.

3. 3

   Disconnect the electrical harness from the sensor.

4. 4

   Repair or replace the affected section of the harness.

   Perform this if the diagnostic checks revealed wiring damage.

5. 5

   Unthread the faulty sensor from the exhaust manifold/tube.

   Perform this if the wiring is intact and no exhaust leaks are present, indicating the sensor itself has likely failed internally.

6. 6

   Clean the mounting port threads and ensure the passageway is free of soot.

7. 7

   Install the new turbine upstream pressure sensor and tighten it to the manufacturer's torque specification.

8. 8

   Reconnect the electrical harness.

9. 9

   Turn the ignition ON (Engine OFF) and use the CNH EST (Electronic Service Tool) or EASY diagnostic tool to clear the fault code.

10. 10

    Start the engine and monitor the exhaust pressure data.

    Ensure the sensor is reading correctly and the fault code does not return.