What does PO 135 diagnostic trouble code on 2005 Chevy Aveo mean?

The PO135 diagnostic trouble code on a 2005 Chevy Aveo indicates a problem with the heated oxygen sensor (HO2S) circuit for the first sensor, typically located before the catalytic converter. This code suggests that the sensor is not heating up as expected, which can lead to poor engine performance and increased emissions. Common causes include a faulty oxygen sensor, wiring issues, or a blown fuse. It's important to diagnose and address this issue to ensure proper engine operation and emissions control.