My AEM wideband gauge shows "SEnS" (sensor failure). What does it mean?

"SEnS" means the gauge detects a sensor error. First check the sensor connector and the harness. If the connections are good, the O2 sensor has failed and must be replaced. A replacement Bosch LSU 4.9-based sensor can be used on AEM X-Series wideband gauges that are set up for the LSU 4.9.