Case IH 3714 – ECU / EDC / ECM: Lambda sensor SRC High error for O2 calibration OR Engine Protection Torque Derate

Depending on the engine platform, this code indicates either an out-of-range high signal or calibration error from the Lambda (O2) sensor (CNH/FPT engines) or an active engine power and speed derate due to a critical emissions/aftertreatment fault (Cummins engines).

• skid steer
• Farmall series tractors
• Farmall 115U Pro EP
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)
• Steiger tractors
• Magnum tractors
• Axial-Flow combines

1. 1

   (Cummins engines - Derate cause) Do not attempt to clear code 3714 directly. Connect a diagnostic tool (like Cummins INSITE or CNH EST) and read all active fault codes to identify the primary root-cause fault code (usually related to the DEF or SCR system).

2. 2

   (CNH/FPT engines - Lambda sensor cause) Inspect the wiring harness leading to the Lambda sensor for chafing, melting, or open/short circuits.

3. 3

   (CNH/FPT engines - Lambda sensor cause) Check the sensor connector for corrosion, pushed-out pins, or moisture intrusion.

4. 4

   (CNH/FPT engines - Lambda sensor cause) Verify battery voltage at the SPI chip (related codes like 3720 indicate low voltage to the sensor).

5. 5

   (CNH/FPT engines - Lambda sensor cause) Inspect the exhaust system upstream of the sensor for leaks, which can introduce outside air and skew O2 calibration readings.

1. 1

   Disconnect battery

   (CNH/FPT engines) Disconnect the negative battery terminal.

2. 2

   Locate and disconnect sensor

   (CNH/FPT engines) Locate the Lambda sensor in the exhaust pipe (upstream of the catalytic converter) and disconnect the 5-pin electrical connector.

3. 3

   Inspect and remove sensor

   (CNH/FPT engines) If wiring is damaged, repair the harness. If the wiring is intact, use an O2 sensor socket to remove the faulty Lambda sensor.

4. 4

   Install new sensor

   (CNH/FPT engines) Apply a small amount of anti-seize to the threads of the new sensor (if not pre-applied) and install it into the exhaust pipe. Torque to OEM specifications.

5. 5

   Reconnect components

   (CNH/FPT engines) Reconnect the electrical connector and the battery.

6. 6

   Clear codes and reset

   (CNH/FPT engines) Use a diagnostic service tool to clear the fault code and reset the learned O2 calibration values if required.

7. 7

   Repair primary fault

   (Cummins engines) Troubleshoot and repair the primary active fault code first (e.g., replace the failed NOx sensor or unclog the DEF dosing valve).

8. 8

   Run system test

   (Cummins engines) Once the physical repair is complete, satisfy the ECM's 'Conditions for Clearing the Fault Code' by running an Aftertreatment Maintenance command or SCR system test via the diagnostic tool.

9. 9

   Perform DPF regeneration

   (Cummins engines) Perform a manual/forced DPF regeneration to get the exhaust system up to operating temperature (the NOx sensors must reach at least 550°F to start reading).

10. 10

    Verify code clears

    (Cummins engines) Once the ECM sees a meaningful reduction in NOx across the SCR and verifies the emissions system is functioning properly, code 3714 will automatically go inactive.

11. 11

    Reflash ECM

    (Cummins engines) If code 3714 remains active with no other active codes present, the ECM is experiencing a software latching issue and must be recalibrated/reflashed with the latest software update to clear the derate.