Powertrain, generic (extended)

P2201 NOx Sensor Circuit Range/Performance (Bank 1 Sensor 1)

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modeNo

Here the upstream NOx sensor on bank 1 is electrically intact, yet its reading is not believable. Manufacturers test this in different ways. VW's 2014 Touareg TDI compares the reading with modelled engine-out NOx (deviation beyond 60 percent), checks a slow fall from 100 to 60 percent (over 4.5 s) and an offset outside +50/-30 ppm. Ford runs a self-test after shutdown and flags an offset above about 20 ppm low or 40 ppm high. GM's 3.0L Duramax (LZ0) watches internal pump-current stability, Type B over two trips. Ford TSBs 24-2136/24-2148 fix 2020-2023 6.7L trucks with a new sensor and software; Volvo and Mack warn that the code often results from another fault and ask for a conversion test first. P229F is the downstream twin.

Likely causes

Aged or poisoned NOx sensing element with offset or slow response

Exhaust leak upstream of the sensor letting in outside air

Fault elsewhere (EGR, fuelling, DEF dosing) that shifts real NOx output

Control software calibration (Ford 6.7L 2020-2023, TSB 24-2136/24-2148)

Symptoms

Malfunction indicator lamp on
Often stored together with SCR efficiency codes such as P20EE
Increased AdBlue consumption or SCR warning

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€100–1,100

Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

nox sensor

References: static.nhtsa.gov, fordservicecontent.com, gsi.ext.gm.com, static.nhtsa.gov.