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

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.

Bank 1 is the side of the engine with cylinder 1. Inline engines only have this bank.

Symptoms

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

Most 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

What to check, in order

Start with the simplest. You can tick off each step.

1. Read the codes and the NOx data before and after the SCR catalyst
2. Compare the reading with other engine data while varying the engine speed.
3. Check the sensor's connector and wiring
4. Look for exhaust leaks ahead of the sensor
5. Confirm that the AdBlue/DEF is of good quality
6. Replace the sensor only after ruling out power, ground, and leaks

Good to know

• Repair difficulty: medium
• It affects emissions.

What each character of P22A7 means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 2: Fuel injection
• A7: Specific fault in that system

Frequently asked questions

Can I keep driving with code P22A7?

You can usually keep driving in the short term, but get it repaired soon: on many diesels, the warning eventually limits starting or engine power.

What causes code P22A7?

The most common causes are: 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).

Related codes

• P22A6NOx Sensor Heater Sense Circuit (Bank 1 Sensor 2)
• P22A8NOx Sensor Heater Sense Circuit Low (Bank 1 Sensor 2)
• P22A9NOx Sensor Heater Sense Circuit High (Bank 1 Sensor 2)
• P22AANOx Sensor Heater Sense Circuit Intermittent (Bank 1 Sensor 2)
• P220FNOx Sensor Heater Control Circuit Range/Performance (Bank 1 Sensor 2)
• P2209NOx Sensor Heater Sense Circuit Range/Performance (Bank 1 Sensor 1)
• U029ELost Communication With NOx Sensor B

Sources

• gsi.ext.gm.com: 25OBDG04A
• gsi.ext.gm.com: 14OBDG04 Engine Diagnostics
• static.nhtsa.gov: MC 10074008 2280
• fordservicecontent.com: obd summary diesel 2023

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.