● Can wait
Usually no immediate risk. Book it in, and watch for new symptoms.
Usually no immediate risk. Book it in, and watch for new symptoms.
The downstream oxygen sensor shows the catalytic converter on bank 1 is not cleaning the exhaust well enough. The driver often notices only the engine light.
Guided check
- Is there another code too, such as a misfire or mixture code?If yes: Fix that code first. A misfire or rich mixture can set this code, and a new catalyst would fail again.
- Is there an exhaust leak near the oxygen sensors?If yes: Repair the leak and clear the code. Air from a leak can give false readings.
- When warm, does the rear sensor swing up and down like the front one?If yes: The catalyst is probably worn. Confirm with a temperature test across it, then quote the replacement.
These checks are general and are still being reviewed by working mechanics.
Causes vary by car. Test before you order a part.
Likely causes, most common first
- Worn catalytic converter
- Exhaust leak near the sensors
- Misfire or rich mixture that damaged the catalyst
- Faulty downstream oxygen sensor
Parts usually involved
- Catalytic converter Find at suppliers
- Oxygen sensor Find at suppliers
- Exhaust gaskets Find at suppliers
Test before you replace
Fix any misfire or fuel trim fault first, then compare upstream and downstream sensor signals and check for exhaust leaks.
General guidance for generic OBD2 codes. Always follow the maker's procedure for the car in front of you.