P2206 – NOx Sensor Heater Control Circuit Low Bank 1 (OBD2)
P2206 means "NOx Sensor Heater Control Circuit Low Bank 1". The voltage the control unit measures in the NOx sensor circuit is below the permitted minimum. For a sensor this usually means the signal wire is shorted to ground or the reference voltage is missing; for an actuator, that its control wire is shorted to ground.
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P2206 quick summary
| Fault code | P2206 |
|---|---|
| Meaning | NOx Sensor Heater Control Circuit Low Bank 1 |
| System | Powertrain (Engine & Transmission) |
| Vehicles | Generic OBD2 |
| Severity | Medium |
| Can I drive? | Usually yes, but the AdBlue system may stop dosing and some vehicles start a countdown before limiting the engine or preventing a restart. Have it repaired soon. |
| Repair cost | €100 – €800 |
How the NOx sensor works
The NOx sensor measures nitrogen oxides in the exhaust so the control unit can run and monitor the SCR (AdBlue) system or NOx storage catalyst; these codes mean the sensor, its heater or its circuit has a fault.
Modern diesels – and some petrol engines with a NOx storage catalyst – have one or two NOx sensors in the exhaust: one before and one after the SCR catalyst. Each sensor has its own small control module on the cable that heats the sensor element and sends the NOx value over the CAN bus.
The engine control unit uses the upstream sensor to calculate how much AdBlue to inject and the downstream sensor to check that the catalyst works. A faulty sensor can therefore cause AdBlue system warnings, a countdown to a no-start on some vehicles and failed emissions tests.
NOx sensors are exposed to high temperatures, condensation and soot. Common faults are a failed heater, a cracked sensor element, a damaged control module or connector and a sensor that is slowly drifting.
Bank 1 is the side of the engine that contains cylinder 1. In-line engines (three, four, five or six cylinders in a row) have only bank 1.
Symptoms of P2206
- Check Engine light
- AdBlue or emission system warning
- Countdown message ("No start in … km")
- Higher AdBlue consumption or no AdBlue consumption
- Failed emissions test
Most common causes of P2206 (most likely first)
Mechanic's Pro Tip
On many vehicles the upstream and downstream NOx sensors look identical but have different part numbers. Check the part number carefully – the wrong sensor causes plausibility codes straight away.
1.Signal or control wire shorted to ground
Most likelyLook for chafed insulation where the harness touches the engine, exhaust brackets or body edges.
2.Missing 5 V reference or supply voltage
An open reference wire or a shorted sensor elsewhere on the same reference circuit can pull it down.
3.Internal short in the NOx sensor
4.Failed NOx sensor element or heater
5.Faulty sensor control module on the cable
6.Corroded or wet connector, damaged wiring near the exhaust
7.Exhaust leak near the sensor
Step-by-step diagnostic guide
- 1
Read codes and NOx values
Read the engine control unit and check both NOx sensor readings and their status (ready, heater on) in live data with a warm engine.
- 2
Measure the signal voltage
With the ignition on and the NOx sensor plugged in, back-probe the signal wire. Then unplug it and check the reference/supply and ground wires separately.
Multimeter: Signal near 0 V = short to ground or no reference. Reference wire: about 5 V with ignition on. Signal wire to ground with connector unplugged: no continuity.
- 3
Check supply and CAN
Check the supply and ground at the sensor control module and look for CAN communication codes.
Multimeter: Most NOx sensor modules are supplied with battery voltage and communicate over CAN; check the specification for your vehicle.
- 4
Inspect connector and wiring
Check the connector for water and corrosion and the cable for heat damage.
- 5
Check for exhaust leaks
Look for leaks near the sensor that let in fresh air.
- 6
Replace and adapt
Replace the sensor (with its control module), clear codes and run any NOx sensor adaptation or system test with the scan tool.
Frequently asked questions
Can I keep driving with P2206?
Usually yes, but the AdBlue system may stop dosing and some vehicles start a countdown before limiting the engine or preventing a restart. Have it repaired soon.
How much does it cost to fix P2206?
Typical repair costs are 100 € – 800 €, depending on the cause and the vehicle. The most common fixes are: signal or control wire shorted to ground; missing 5 V reference or supply voltage; internal short in the NOx sensor. Always confirm the cause with the tests above before buying parts.
Can I drive with a NOx sensor fault?
Usually for a while, but many diesels start a countdown and then limit power or prevent a restart. Repair it before the countdown ends.
Can a NOx sensor be cleaned?
No. If the sensor or its heater has failed, it must be replaced.
What is the difference between P2206 and similar codes?
P2206 belongs to a group of codes for the same component that differ in the type or location of the fault: P2201 – NOx Sensor Range/Performance Bank 1; P2202 – NOx Sensor Circuit Low Bank 1; P2203 – NOx Sensor Circuit High Bank 1; P2204 – NOx Sensor Circuit Intermittent Bank 1; P2205 – NOx Sensor Heater Control Circuit/Open Bank 1; P2207 – NOx Sensor Heater Control Circuit High Bank 1. The tests on this page apply to the whole group; the type of fault tells you where to start.
Related fault codes
This guide is for information only. Working on vehicles can be dangerous — if you are unsure, have the car checked by a qualified mechanic. Values can differ between model years; always check the manufacturer's repair information.