P22A7

Code

Generic P — Powertrain

NOx Sensor Heater Sense Circuit Range/Performance Bank 1 Sensor 2

Brand: Generic

Type: P — Powertrain

Views: UK: 21 EN: 103 RU: 52

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Page language: EN

Causes

Open or short in the NOx sensor heater wiring or connector (Bank 1 Sensor 2)
Corroded, loose, or pushed‑out connector pins at the sensor or harness
Failed NOx sensor (heater element or internal sense circuit)
Blown fuse or faulty relay supplying the heater circuit
PCM or power/ground fault to the heater control/sense circuit
Damage from heat, road debris, or oil/contaminant exposure

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
Possible reduced aftertreatment performance, increased NOx emissions
Limp or derate strategy on some vehicles during severe faults
Other aftertreatment or NOx‑related codes present
Occasional hard starting or poor driveability in extreme cases

What to check

Retrieve freeze‑frame and snapshot data from the scan tool; note related codes and operating conditions
Visual inspection of sensor, harness and connector for damage, corrosion, melted insulation or heat exposure
Check fuses and relays related to the NOx sensor heater circuit
Backprobe and monitor heater control and heater sense signals with a scan tool or multimeter
Measure heater resistance (with harness disconnected) using a DMM
Wiggle test wiring while monitoring live data for intermittent changes

Signal parameters

Heater resistance (sensor removed/disconnected): typically low ohms — commonly in the single‑ to low‑double digit ohms (vehicle dependent).
Heater supply/control: usually battery voltage or PWM switching from PCM (0–12 V range depending on vehicle).
Heater current (when commanded ON): may be in the range of hundreds of milliamps to several amps depending on sensor design.
Sense feedback (if applicable): a low‑voltage feedback or sense line that should correlate to heater state; should not be open or showing erratic values.

Diagnostic algorithm

Read all stored DTCs and freeze‑frame data. Note whether code is current or historic and any other related aftertreatment or heater codes.
Perform a thorough visual inspection of the NOx sensor (Bank 1 Sensor 2) and wiring from the sensor to the main harness and PCM. Look for heat damage, chafing, disconnected pins, corrosion, or melted insulation.
Check fuses and relays for the sensor heater circuit; replace if blown/faulty and retest.
With the engine OFF and connector disconnected, measure heater element resistance at the sensor pins with a DMM. Compare to typical range from manufacturer data; an open or very high reading indicates a failed heater.
Reconnect and, with a scan tool, command the heater ON (if supported) while monitoring heater voltage and current. Alternatively measure heater supply voltage at the connector while heater is commanded ON. Confirm supply and PWM activity and that sense line behavior matches expected heater state.
If supply is present but the sensor heater is open or out of range, replace the NOx sensor. If supply is missing or shorted, trace wiring back toward fuse/relay/PCM looking for shorts to ground or open circuits; repair wiring or connector damage.
Perform wiggle tests and monitor live data for intermittent faults. If intermittent and not reproducible, use a scope to examine PWM/sense signals under load and during normal driving conditions.
After repair or replacement, clear codes, perform required relearn/initialization if applicable, and run a drive cycle or forced regeneration/verification procedure to confirm the fault does not return.

Likely causes

Broken or shorted heater supply or sense wire caused by heat damage near the exhaust
Bad sensor heater element (high resistance or open)
Corroded connector causing high resistance in the sense lead
Blown inline fuse for the NOx heater circuit