Emissions

P2205 — NOx Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

Severity: medium Drive with care, to a shop

What P2205 means

The NOx sensor measures nitrogen oxides in the exhaust and only works once it reaches operating temperature, so it has a built-in heater. The control unit monitors the heater circuit and saw a voltage that is too low, which usually points to a short to ground or a failed heater element. Until the sensor is warm, its readings are unreliable and the SCR system cannot dose reductant accurately.

Symptoms

  • Check engine light or SCR/AdBlue warning on
  • SCR system inactive on cold start
  • NOx readings invalid until the engine is warm
  • Start countdown on some vehicles
  • Possible power or torque limitation

Possible causes

  1. Failed heater element inside the NOx sensor
  2. Heater circuit shorted to ground
  3. Blown fuse for the NOx sensor heater
  4. Damaged wiring or corroded connector
  5. Faulty NOx sensor or its control module

How to diagnose

  1. Scan all codes and freeze frame data, and note any other SCR or NOx codes
  2. View NOx sensor values and dosing system status on a scan tool
  3. Check reductant (DEF/AdBlue) level and quality
  4. Check the fuse supplying the NOx sensor heater
  5. Inspect the harness and connector for chafing, moisture, corrosion and shorts to ground
  6. Measure heater resistance and supply voltage at the connector
  7. Inspect the dosing valve, lines and other SCR components
  8. Look for manufacturer technical bulletins and software updates

Common fixes

  • Replace the fuse after finding why it blew
  • Repair the wiring or connector in the heater circuit
  • Replace the NOx sensor
  • Update the control unit software if a bulletin calls for it
  • Clear codes and confirm the SCR system operates normally

Questions and answers

What does P2205 mean?

The control unit sees a low signal in the Bank 1 NOx sensor heater circuit. The most common causes are the sensor itself, a short to ground, or a blown fuse.

Can I drive with P2205?

For a short time, yes, but emissions are above normal and some vehicles will limit power and count down starts. Get it diagnosed soon.

Do I always need a new NOx sensor?

No. Check the fuse, wiring and connector first. Replace the sensor if power and wiring are good but the heater has failed.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.