P0422

Catalyst 2 Efficiency Below Threshold Bank 1

Q: Is it safe to drive with P0422?

Yes, the car drives normally. But it's exceeding emissions limits and won't pass inspection, and an underlying misfire or rich condition can worsen over time, so address it.

Q: Can I just clear P0422?

It will return after a drive cycle or two unless the converter or the condition that hurt it is repaired.

Catalyst / emissions Generic OBD-II Medium

What it means

P0422 means the catalytic converter on bank 1 isn't cleaning the exhaust as well as it should — the computer compares the upstream and downstream oxygen sensors and sees efficiency below the limit. The car usually drives normally, but it's emitting more pollutants than allowed. Before replacing an expensive converter, rule out O2-sensor faults, exhaust leaks, and any misfire or fuel issue that could have damaged it.

Medium

Can I keep driving? You can keep driving. The car runs normally, but it's polluting more than allowed and will fail an emissions test until the cause is fixed.

Real-world scan data

Seen in

scans in the past year

Found in

<0.1%

of scans

<0.1%

of scans that found faults

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Check-engine light on
Failed emissions test
Slightly reduced fuel economy
Occasionally a faint sulfur (rotten-egg) smell from the exhaust

Common causes

Most likely first

Aged or failing catalytic converter (bank 1)Likely
Faulty or lazy downstream oxygen sensor giving a misleading readingCommon
Exhaust leak near the sensors skewing the readingsCommon
Upstream problem — misfire or rich/lean running — that damaged the converterLess often
Failed ECM (rare — verify everything else first)Less often

How to diagnose & fix

Work through it in order

Read freeze-frame data and check for any misfire, fuel-trim, or O2-sensor codes first — fix those before condemning the converter.
Compare the upstream and downstream O2 sensor waveforms; a downstream sensor that mirrors the upstream one points to a worn converter.
Inspect the exhaust for leaks between and around the sensors.
Confirm the engine isn't running rich or misfiring and that fuel trims are normal.
If the converter is genuinely worn out, replace it, then clear and re-test.

FAQ

Quick answers

Is it safe to drive with P0422?+

Yes, the car drives normally. But it's exceeding emissions limits and won't pass inspection, and an underlying misfire or rich condition can worsen over time, so address it.

Can I just clear P0422?+

It will return after a drive cycle or two unless the converter or the condition that hurt it is repaired.

Read & clear P0422 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX