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Home / DTC / P22A7 — NOx Sensor Heater Sense Circuit Range/Performance Bank 1 Sensor 2

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

Detailed page for trouble code P22A7.

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Code

P22A7

Generic P — Powertrain

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

Brand: Generic
Type: P — Powertrain
Views: UK: 10 EN: 16 RU: 29
AI status
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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

  1. Read all stored DTCs and freeze‑frame data. Note whether code is current or historic and any other related aftertreatment or heater codes.
  2. 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.
  3. Check fuses and relays for the sensor heater circuit; replace if blown/faulty and retest.
  4. 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.
  5. 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.
  6. 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.
  7. 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.
  8. 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

Fault status

⚠️ Status
NOx sensor heater sense circuit out of range/performance — Bank 1 Sensor 2
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

P22A6 P22A8 P2201 P2196
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