Emissions

P2209 — NOx Sensor Positive Current Control Circuit Open (Bank 1 Sensor 1)

Severity: medium Drive with care, to a shop

What P2209 means

The engine or NOx sensor control module monitors the circuit that sets the positive current in the nitrogen oxide sensor's measuring cell. This sensor sits in the exhaust and helps the control unit judge how well the SCR (urea/AdBlue) system is working. With P2209 the current control circuit reads as open, so the cell isn't working and the sensor's readings can't be trusted.

Symptoms

  • Check engine light or SCR/AdBlue warning on
  • SCR system inactive and urea dosing disabled
  • Other NOx sensor codes set at the same time
  • Start countdown on some vehicles
  • Possible torque limitation

Possible causes

  1. Failed electronics inside the NOx sensor
  2. Open control wire or poor connector contact
  3. Corroded or damaged connector and harness
  4. Faulty SCR control module or NOx sensor module
  5. Control unit software fault

How to diagnose

  1. Read all codes and freeze frame data and note related NOx and SCR codes
  2. View NOx sensor values and dosing system status on a scan tool
  3. Check reductant (AdBlue) level and quality
  4. Inspect the sensor connector and harness for chafing, corrosion, moisture or heat damage
  5. Test the control circuit wiring for opens and shorts to ground, and check sensor power and ground
  6. Check the dosing valve, lines and heater operation
  7. Look for technical bulletins and software updates for the vehicle
  8. Clear codes after repair and confirm they don't return

Common fixes

  • Repair the open wire or replace the damaged harness
  • Clean or replace a corroded connector
  • Replace the NOx sensor
  • Replace or reprogram the SCR or sensor control module
  • Install the manufacturer's software update

Questions and answers

What does P2209 mean?

It means the control unit detected an open in the NOx sensor positive current control circuit on bank 1. The sensor can't work properly, so the SCR system loses its NOx data.

Can I drive with P2209?

For a short time, yes, but emissions will be higher and some vehicles will limit power or start a restart countdown. Get it diagnosed soon.

Do I always need a new NOx sensor?

No. Check the connector, wiring and power supply first, since an open wire or corroded contact can cause this. If the wiring is good, the sensor itself is the most likely culprit.

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.