OBD-II code · Emissions / Engine
The downstream oxygen sensor sees the catalytic converter storing less oxygen than expected. That can mean a tired converter — but a lazy sensor, an exhaust leak, or a misfiring cylinder dumping raw fuel into the cat produces the exact same code.
Quote a new catalytic converter ($1,200–$2,500 installed) without checking sensor response first. If the real culprit was a $60 sensor or a $40 exhaust gasket, the code returns after you have paid.
Typical guess-and-swap cost: $1,200–$2,500 (converter) when the cat is not the fault
Compare upstream vs downstream O2 waveforms on live data at operating temperature, check for exhaust leaks and misfire counters, verify fuel trims. A converter diagnosis takes 20 minutes of live data — and tells you which part is actually done.
Mobile service in Canyon Lake, San Antonio & Austin. Written report with root cause — see a sample.