What causes a p0135 code?

Answer 1

The P0135 code indicates a problem with the oxygen sensor circuit for Bank 1, specifically the heater circuit of the upstream oxygen sensor. Common causes include a faulty oxygen sensor, issues with the sensor's wiring or connectors, or a malfunctioning engine control module (ECM). Additionally, problems such as blown fuses or insufficient power supply to the sensor's heater can also trigger this code. Proper diagnosis is essential to pinpoint the exact cause.