Case IH 3715 – Engine Control Unit (Engine ECU / EDC): Lambda sensor: Fault code to indicate SRC Low error for O2 calibration

The engine's control system has detected that the source voltage or signal from the Lambda (Oxygen/O2) sensor is lower than the minimum acceptable threshold during its calibration phase.

• Farmall
• Farmall 115U Pro EP
• Puma 210
• Maxxum
• Magnum
• Optum
• Luxxum
• SR175

1. 1

   Check the battery and system voltage (low battery voltage at the SPI chip can trigger Lambda sensor errors)

2. 2

   Inspect the Lambda sensor wiring harness and connector for open circuits or shorts to ground

3. 3

   Inspect the exhaust system near the sensor for leaks that could introduce outside air and skew O2 calibration readings

4. 4

   Check the sensor's internal resistance (the ECU monitors inner resistance calibration values)

1. 1

   Turn off the engine and disconnect the battery

   This ensures safety and prevents electrical shorts.

2. 2

   Locate the Lambda sensor on the exhaust system

   Typically mounted near the Diesel Particulate Filter (DPF) or muffler.

3. 3

   Disconnect the electrical connector for the Lambda sensor

4. 4

   Loosen or remove the exhaust system heat shield

   Perform this if necessary to gain access to the sensor.

5. 5

   Unscrew the Lambda sensor from the exhaust pipe

   Carefully remove it using an O2 sensor socket or wrench.

6. 6

   Install the new Lambda sensor

   The M18x1.5 threaded sensor must be torqued to the manufacturer specification of 45 to 55 Nm.

7. 7

   Reconnect the electrical harness and reinstall any heat shields

8. 8

   Reconnect the battery

9. 9

   Connect a diagnostic tool and perform the 'Reset ECU data (Lambda sensor)' or O2 calibration routine

   Use a tool such as the Case IH Electronic Service Tool or Bosch ESI[truck] to initialize the new sensor.