Case IH 3949 – Engine ECU: EGR Lift Sensor 1 Signal Too Low

The voltage returning from the EGR lift sensor to the ECU has dropped below the minimum acceptable threshold (typically 0.3 Volts or lower). When this code is triggered, the system will automatically stop EGR operation to prevent incorrect emissions control or engine damage, and an Amber warning light is illuminated.

• skid steer
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)
• SR175
• TV620B
• Steiger series tractors
• Maxxum series tractors

1. 1

   Check Battery Voltage: Ensure the machine's overall battery voltage is normal, as low system voltage can cause sensor dropouts.

2. 2

   Check Sensor Supply Voltage: Verify that the 5V reference voltage (VCC6) is reaching the EGR lift sensor.

3. 3

   Inspect the Wiring Harness: Check the wiring between the Engine ECU and the EGR lift sensor for an open circuit or a short to ground.

4. 4

   Monitor Live Data: If you have a diagnostic tool (like CNH EST), monitor the 'EGR lift sensor volt %' and 'Target EGR position' while the engine is running to see if the sensor is completely dead or just sticking.

1. 1

   Access the EGR Valve

   Locate the EGR valve assembly on the engine block. The lift sensor is typically mounted directly to the top or side of the EGR valve housing.

2. 2

   Test the Circuit

   Disconnect the EGR lift sensor pigtail. Using a multimeter, test the harness side for proper reference voltage and ground.

3. 3

   Repair Wiring (If Applicable)

   If there is no reference voltage or there is continuity to ground on the signal wire, trace the harness back to the Engine ECU and repair the broken or chafed wire.

4. 4

   Replace the Sensor

   If the wiring tests good, the sensor itself has failed internally. Remove the mounting screws holding the EGR lift sensor to the valve and install the new sensor. (Note: On some engine models, the sensor is integrated into the EGR valve, requiring the replacement of the entire EGR valve assembly).

5. 5

   Relearn Procedure

   After replacing the sensor or valve, clear the fault codes. You may need to run the engine on idle for a few minutes or perform a test drive to allow the ECU to relearn the EGR closed position.