Cause
Aging or slow oxygen sensor
An oxygen sensor whose response has slowed with age rather than failed outright. This is honest wear: the sensor lives at several hundred degrees in a corrosive gas stream and switches millions of times, and its transitions get gradually lazier over tens of thousands of miles.
The distinction that decides the repair is slow versus delayed. Slow response is about the rate of the transition — it starts when it should and takes too long to get there, which is ageing. Delayed response is dead time — it does not begin moving until well after the mixture changed, which is usually an exhaust leak, a sensor out of the gas stream, or a fouled shield. Ageing does not produce dead time, so a delayed-response code on a low-mileage sensor is asking a different question.
Position decides urgency. An upstream sensor controls the fuelling, so a lazy one makes the mixture swing wider than intended and costs economy continuously. A downstream sensor only judges the catalytic converter, so a lazy one blocks emissions monitoring while the car drives normally.
Premature ageing is a symptom, not a verdict. A sensor lazy well before its time was poisoned by something — oil, coolant, or silicone from non-approved sealant — and a replacement fitted into the same exhaust meets the same contamination.
Typically a moderate job.
Codes this can cause (12)
Codes where this is a likely explanation first, rather than merely a possible one.
- P013A O2 Sensor Slow Response - Rich to Lean Bank 1 Sensor 2 Likely for this code Moderate
- P013E O2 Sensor Delayed Response - Rich to Lean Bank 1 Sensor 2 Likely for this code Moderate
- P013F O2 Sensor Delayed Response - Lean to Rich Bank 1 Sensor 2 Likely for this code Moderate
- P014A O2 Sensor Delayed Response - Rich to Lean Bank 2 Sensor 2 Likely for this code Moderate
- P014B O2 Sensor Delayed Response - Lean to Rich Bank 2 Sensor 2 Likely for this code Moderate
- P015A O2 Sensor Delayed Response - Rich to Lean Bank 1 Sensor 1 Likely for this code Moderate
- P015C O2 Sensor Delayed Response - Rich to Lean Bank 2 Sensor 1 Likely for this code Moderate
- P015D O2 Sensor Delayed Response - Lean to Rich Bank 2 Sensor 1 Likely for this code Moderate
- P2297 O2 Sensor Out of Range During Deceleration Bank 1 Sensor 1 Likely for this code Moderate
- P2298 O2 Sensor Out of Range During Deceleration Bank 2 Sensor 1 Likely for this code Moderate
- P015E Excessive Time to Enter Closed Loop Fuel Timing Control Moderate
- P016A Excessive Time To Enter Closed Loop Air/Fuel Ratio Control Moderate
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Others who found this
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
Sign in or create an account to add what you found about Aging or slow oxygen sensor.