Case IH 3715 – ENGINE Controller: Lambda sensor: SRC Low error for O2 calibration

The Engine Control Module has detected that the Signal Range Check (SRC) for the exhaust oxygen (O2) sensor's calibration is too low. The system is unable to properly calibrate the sensor's readings, which is usually caused by a failing sensor, a wiring issue, or an exhaust anomaly.

• skid steer
• Farmall series tractors
• Farmall 115U Pro EP
• Farmall 105A
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)
• Maxxum series tractors
• Puma series tractors

1. 1

   Check battery and supply voltage, as low voltage at the SPI chip can trigger Lambda sensor faults

2. 2

   Inspect the wiring harness and connector leading to the Lambda sensor for chafed wires, melted insulation, or corroded pins

3. 3

   Inspect the exhaust piping upstream of the Lambda sensor for soot trails or leaks that could introduce outside air and skew O2 readings

4. 4

   Connect the CNH Electronic Service Tool (EST) to monitor the Lambda sensor's inner resistance and live voltage to determine if the sensor is dead or stuck at a low voltage

1. 1

   Power Down

   Turn off the machine, remove the key, and disconnect the negative battery cable to prevent electrical shorts.

2. 2

   Locate the Sensor

   Locate the Lambda (O2) sensor on the exhaust system. It is typically threaded into the exhaust pipe downstream of the turbocharger or near the DPF/DOC assembly.

3. 3

   Remove the Sensor

   Disconnect the sensor's electrical pigtail from the main engine harness. Use a specialized O2 sensor socket (usually 22mm or 7/8") to carefully unthread the sensor from the exhaust bung. Tip: If the sensor is seized, apply penetrating oil and allow the exhaust to warm up slightly before attempting removal.

4. 4

   Install the New Sensor

   Apply a small amount of anti-seize compound to the threads of the new Lambda sensor (if it doesn't already come pre-coated). Thread it in by hand to avoid cross-threading, then torque it to the manufacturer's specification.

5. 5

   Reconnect

   Plug the sensor's electrical connector back into the engine harness and reconnect the battery.

6. 6

   Recalibrate / Clear Codes

   Connect the CNH EST diagnostic laptop. Clear the inactive 3715 fault code. Navigate to the engine controller configuration menu and perform the "Reset ECU data (Lambda sensor)" routine so the ECM learns the calibration values of the new sensor.