Powertrain, generic (extended)

P22A7 NOx Sensor Heater Sense Circuit Range/Performance (Bank 1 Sensor 2)

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modeNo

P22A7 means the heater feedback of the rear NOx sensor on bank 1 shows a heater that does not reach or hold its target, although no open or short is found. GM's 3.0L LZ0 and 2017 small diesels compare the measured heater resistance with its target once supply has been in range for 45 s and dew point passed 180 s ago (Type B); the 6.6L LML fails the sensor if its heater never reports set-point temperature. VW's 2014 Touareg TDI allows 180 s after dew point; Ford uses the code as a signal readiness check. Ford traced it on 2017 to 2020 6.7L Super Duty trucks to water in the NOx connectors (TSB 20-2067, new harness 14406) and on 2023 models to that harness chafing on the EGR cooler, with fuse F18 blown (SSM 51750/51791). Nissan's NTB16-048 replaces the outlet sensor.

Likely causes

Aged heater or element in the outlet NOx probe

Water in the NOx sensor connectors (Ford 6.7L 2017-2020, TSB 20-2067)

Harness chafed on the EGR cooler with blown supply fuse (Ford 6.7L 2023)

Weak supply to the sensor module limiting heater power

Symptoms

Malfunction indicator lamp on
Outlet NOx sensor becomes ready late or not at all
Often stored with U029E or other NOx sensor codes

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€50–1,000

Time0.5–3 h

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

Parts involved

nox sensornox sensor heaternox sensor wiring

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