Case IH 3711 – ENGINE: Lambda Sensor: SCB Error of the LSU Heater Power stage

The engine computer has detected a short circuit to battery voltage on the circuit that powers the internal heating element of the Lambda (wideband O2) sensor.

• skid steer
• Maxxum
• Puma
• Magnum
• Steiger
• SR130
• SR160
• SR175
• SV series

1. 1

   Inspect the Lambda sensor wiring harness and connectors for melted insulation, chafed wires touching a power source, or damaged pins that could cause a short to battery voltage.

2. 2

   Disconnect the Lambda sensor and perform a harness voltage test with the key ON (engine off). Probe the heater power supply pins on the harness side to verify voltage is only present when commanded by the ECU and that ground/return circuits are not shorted to a 12V source.

3. 3

   Measure the resistance of the heating element pins directly on the sensor. If the resistance is out of specification or shows a dead short, the sensor's internal heater has failed.

4. 4

   Check the fuses or relays associated with the engine sensor heating circuits to ensure a short hasn't blown a protective fuse.

1. 1

   Turn off the ignition switch and disconnect the battery ground cable to prevent electrical spikes.

   Turn off the ignition switch and disconnect the battery ground cable to prevent electrical spikes.

2. 2

   Locate the Lambda sensor on the exhaust system.

   Locate the Lambda sensor on the exhaust system (typically mounted on the exhaust pipe near the turbocharger outlet or before the aftertreatment/DOC unit).

3. 3

   Disconnect the sensor's electrical connector.

   Disconnect the sensor's electrical connector.

4. 4

   Unscrew the faulty Lambda sensor from the exhaust pipe.

   Using an O2 sensor socket or wrench, carefully unscrew the faulty Lambda sensor from the exhaust pipe.

5. 5

   Prepare the new sensor.

   If the threads do not have pre-applied anti-seize compound, apply a small amount of high-temp, sensor-safe anti-seize to the threads. Caution: Do not get any compound on the sensor tip, as this will contaminate and ruin the sensor.

6. 6

   Thread the new sensor into the exhaust pipe.

   Thread the new sensor into the exhaust pipe by hand to prevent cross-threading, then tighten it to the manufacturer's specified torque.

7. 7

   Reconnect the electrical harness.

   Reconnect the electrical harness. Ensure the wire is routed safely away from extreme exhaust heat and moving parts.

8. 8

   Reconnect the battery ground cable.

   Reconnect the battery ground cable.

9. 9

   Clear the inactive fault code and verify the repair.

   Turn the key on and use a diagnostic tool (such as the CNH EST or Jaltest) to clear the inactive fault code from the ECU. Start the engine and verify the code does not return.