O2 Sensor Circuit Slow Response (Bank 1 Sensor 2)
What it means
The engine computer has found that the downstream oxygen sensor on bank 1 is slow to change its reading when the mixture changes, often tested during fuel cut on deceleration. The usual cause is an aged sensor; the code rarely affects how the engine runs, but it disables catalytic converter monitoring.
Related lights
Dashboard lights that may come on with this code.
Symptoms4
- Check engine light on.
- Usually no noticeable driving symptoms.
- Catalytic converter self-test does not complete.
- Failed emissions test.
Possible causes5
- Aged downstream oxygen sensor.
- Sensor contaminated by engine oil or coolant.
- Exhaust leak near the sensor.
- Weak sensor heater.
- Extra resistance in the connector or wiring.
How to diagnose5
- Watch the downstream signal when lifting off the accelerator at speed, then under hard acceleration; a good sensor moves between the two readings quickly.
- Compare the response with manufacturer data or with the self-test results on the scan tool if available.
- Check the exhaust for leaks near the sensor.
- Make sure there is no heater code such as P0141.
- Inspect the connector for corrosion.
How to fix5
- Repair any exhaust leak.
- Clean the connector or repair the wiring.
- Fix any oil burning or coolant leak before fitting a new sensor.
- Replace the downstream oxygen sensor, the usual fix.
- Clear the codes and drive until the self-test completes.
Repair cost
In Saudi riyals; the highlighted part is the expected range for this fault.
In the Saudi market: SAR 150–900 (≈ USD 40–240)
Our prices come from the Saudi market, converted at a fixed rate (SAR 3.75 per USD). Prices in your country may differ a lot, so we show the cost level.
The price mainly depends on the downstream sensor itself and how hard it is to remove, and rises if an exhaust leak also needs repair.
Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026
Frequently asked questions
Does this code raise fuel consumption?
Usually not, because the downstream sensor monitors the converter and has only a small influence on the mixture.
Why is the sensor tested during deceleration?
Because the computer cuts fuel at that moment, so the exhaust becomes oxygen-rich air, and the computer measures how long the sensor takes to react.
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