P0133: O2 sensor circuit slow response (bank 1) sensor 1
The oxygen sensor in front of the catalytic converter reacts too slowly to changes in the exhaust, so the engine computer can’t correct the fuel mixture as precisely.
Updated
What P0133 means
The oxygen sensor in front of the catalytic converter (sensor 1) tells the engine computer whether the mixture burnt rich or lean. On most petrol engines the computer keeps steering the mixture slightly to either side of the ideal, and the sensor should follow quickly.
The computer measures how quickly it follows. When it’s too slow, it stores P0133 for bank 1.
P0153, and the other slow-response codes
P0153 is the same test on the front sensor of bank 2, on V and flat engines. When both are stored, look for something that affects both sensors, such as oil or coolant reaching the exhaust.
P014C to P014F are the same test split by direction: the front sensor is slow to follow a change from rich to lean, or from lean to rich.
P0139, P0145, P0159 and P0165, and P013A to P013D, are slow-response codes for the sensors behind the catalytic converter (sensor 2, or sensor 3 on some cars). Those sensors mainly check the converter, so the car usually drives as before. The causes and checks are the same.
P0153: O2 sensor circuit slow response (bank 2) sensor 1
P014C: O2 Sensor Slow Response - Rich to Lean Bank 1 Sensor 1
P014D: O2 Sensor Slow Response - Lean to Rich Bank 1 Sensor 1
P014E: O2 Sensor Slow Response - Rich to Lean Bank 2 Sensor 1
P014F: O2 Sensor Slow Response - Lean to Rich Bank 2 Sensor 1
P0139: O2 sensor circuit slow response (bank 1) sensor 2
An oxygen sensor behind the catalytic converter reacts too slowly to changes in the exhaust. The engine computer uses this sensor mainly to check the catalytic converter, and on many cars to fine-tune the mixture.
Common causes: aged or contaminated oxygen sensor, exhaust leak near the sensor, wiring or connector fault.
P0145: O2 Sensor Circuit Slow Response Bank 1 Sensor 3
An oxygen sensor behind the catalytic converter reacts too slowly to changes in the exhaust. The engine computer uses this sensor mainly to check the catalytic converter, and on many cars to fine-tune the mixture.
Common causes: aged or contaminated oxygen sensor, exhaust leak near the sensor, wiring or connector fault.
P0159: O2 Sensor Circuit Slow Response Bank 2 Sensor 2
An oxygen sensor behind the catalytic converter reacts too slowly to changes in the exhaust. The engine computer uses this sensor mainly to check the catalytic converter, and on many cars to fine-tune the mixture.
Common causes: aged or contaminated oxygen sensor, exhaust leak near the sensor, wiring or connector fault.
P0165: O2 Sensor Circuit Slow Response Bank 2 Sensor 3
An oxygen sensor behind the catalytic converter reacts too slowly to changes in the exhaust. The engine computer uses this sensor mainly to check the catalytic converter, and on many cars to fine-tune the mixture.
Common causes: aged or contaminated oxygen sensor, exhaust leak near the sensor, wiring or connector fault.
P013A: O2 Sensor Slow Response - Rich to Lean Bank 1 Sensor 2
An oxygen sensor behind the catalytic converter reacts too slowly to changes in the exhaust. The engine computer uses this sensor mainly to check the catalytic converter, and on many cars to fine-tune the mixture.
Common causes: aged or contaminated oxygen sensor, exhaust leak near the sensor, wiring or connector fault.
P013B: O2 Sensor Slow Response - Lean to Rich Bank 1 Sensor 2
An oxygen sensor behind the catalytic converter reacts too slowly to changes in the exhaust. The engine computer uses this sensor mainly to check the catalytic converter, and on many cars to fine-tune the mixture.
Common causes: aged or contaminated oxygen sensor, exhaust leak near the sensor, wiring or connector fault.
P013C: O2 Sensor Slow Response - Rich to Lean Bank 2 Sensor 2
An oxygen sensor behind the catalytic converter reacts too slowly to changes in the exhaust. The engine computer uses this sensor mainly to check the catalytic converter, and on many cars to fine-tune the mixture.
Common causes: aged or contaminated oxygen sensor, exhaust leak near the sensor, wiring or connector fault.
P013D: O2 Sensor Slow Response - Lean to Rich Bank 2 Sensor 2
An oxygen sensor behind the catalytic converter reacts too slowly to changes in the exhaust. The engine computer uses this sensor mainly to check the catalytic converter, and on many cars to fine-tune the mixture.
Common causes: aged or contaminated oxygen sensor, exhaust leak near the sensor, wiring or connector fault.
Can I keep driving?
Check soon
Probably OK to drive short-term, but have it checked soon. Fuel use or emissions may be worse.
General guidance based on the code alone, not on the car’s actual condition. If in doubt, stop and ask a mechanic.
The engine usually runs normally, but fuel use and emissions can rise, and a slow sensor can also upset the catalytic converter test (P0420).
Symptoms
- Often just the check engine light.
- Higher fuel use on some cars.
- Other codes, such as fuel mixture or catalytic converter codes.
Common causes
- Aged or contaminated oxygen sensor. Sensors slow down with age. Oil or coolant burning in the engine, or unsuitable sealant, can coat them.
- Exhaust leak near the sensor. Outside air drawn in near the sensor upsets its reading.
- Wiring or connector fault. Heat from the exhaust can damage the wiring and connector.
Typical fixes
- Check the exhaust in front of the sensor for leaks.
- Check the sensor’s wiring and connector.
- Look at the front oxygen sensor in live data on a warm engine, if your car reports it: see the live data guide.
- Replace the sensor with the type specified for your car. If oil or coolant is being burnt, fix that first, or the new sensor will suffer too.
Questions
Can I drive with P0133?
Probably for a short time, but have it checked soon: the app’s advice is that fuel use or emissions may be worse.
Does P0133 mean the sensor must be replaced?
Often, but not always. An exhaust leak or a wiring fault can set the same code, and both are worth ruling out first.