P2201

NOx Sensor Circuit Range/Performance Bank 1 Sensor 1

Emissions (NOx / SCR) Generic OBD-II Medium

What it means

P2201 means the bank 1 upstream NOx sensor is giving a reading that's out of its expected range or responding poorly. This sensor measures nitrogen-oxide levels so the ECM can manage the SCR/emissions system, and an implausible signal usually points to a failing sensor, a wiring fault, or an exhaust leak. The engine still runs, but emissions suffer and some diesels can eventually derate power.

Medium

Can I keep driving? Usually drivable, but on many diesels a failing NOx sensor triggers emissions warnings and can lead to a reduced-power derate; address it before that happens.

Real-world scan data

Seen in

857

scans in the past year

Found in

0.1%

of scans

0.2%

of scans that found faults

Appears alongside · share of P2201 scans

P2200in 83.3% of scans

P229Fin 66.4% of scans

P0704in 65.5% of scans

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
Higher tailpipe emissions or a failed emissions test
Possible increased DEF/reductant consumption or SCR warnings (diesel)
Reduced-power derate if the fault escalates (diesel)

Common causes

Most likely first

Faulty NOx sensor (bank 1, upstream)Likely
NOx sensor wiring harness open, shorted, or chafedCommon
Poor connection or corrosion at the NOx sensor connectorCommon
Exhaust leak upstream of the sensor skewing its readingLess often

How to diagnose & fix

Work through it in order

Read freeze-frame data and check for companion NOx or SCR codes (P2200, P2202).
Inspect the NOx sensor connector and wiring for damage, corrosion, or a loose pin.
Check for exhaust leaks near the sensor that could throw off its measurement.
Compare the sensor's live reading against expected values; a stuck or out-of-range signal confirms the sensor.
Replace the NOx sensor if it fails testing, then clear and re-run the monitor.

FAQ

Quick answers

Is it safe to drive with P2201?+

The engine runs normally at first, but emissions are affected and some diesels will eventually reduce power to force a repair, so don't ignore it.

Can I just clear P2201?+

It will clear, but a range/performance fault returns once the emissions monitor runs again unless the sensor or wiring is fixed.

Read & clear P2201 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