What does P2202 mean?
NOx sensors measure nitrogen oxides before and after the SCR catalyst. The computer uses them to dose DEF and to check that the SCR system is working.
The computer is seeing a signal voltage that is lower than the sensor should ever produce, so it is almost always an electrical problem rather than a mechanical one.
Codes are a starting point. They tell you which test failed, not which part to replace. Check for other stored codes and fix those in a sensible order.
Symptoms
- Check engine light
- DEF/emissions warning message
- Possible speed limit countdown (derate)
Common causes
- Open in the 5 V reference wire
- Signal wire shorted to ground
- Unplugged or corroded connector
- Failed sensor
How to diagnose P2202
- With the key on, back-probe the connector: you should see about 5 V on the reference wire and a good ground (under 0.1 V drop).
- If reference and ground are good, check the signal wire for a short to ground with the connector unplugged.
- If the wiring checks out, the sensor itself is the likely fault.
- Check for exhaust leaks.
- Look at NOx sensor readings with a capable scan tool.
How to fix it
- Replace the NOx sensor
- Repair wiring
- Repair exhaust leaks
Estimated repair cost
Likely repairs for P2202 run from about $400 to $1,000, depending on the cause.
| Repair | Typical range (parts + labor) |
|---|---|
| Diagnostic fee (scan + testing) | $100 - $200 |
| NOx sensor replacement (one) | $400 - $1,000 |
These are rough US estimates for an independent shop in 2026, based on typical parts prices and standard labor times. Dealers, big trucks, luxury brands and high-cost areas often run higher. They are not quotes. Use the repair cost estimator to adjust for your vehicle.
How serious is P2202?
High severity
Watch the dash. Many diesels start a speed-limit countdown for SCR faults, so get it in soon.
P2202 FAQ
What does P2202 mean?
P2202 stands for "NOx Sensor Circuit Low (Bank 1)". NOx sensors measure nitrogen oxides before and after the SCR catalyst.
Can I drive with a P2202 code?
Watch the dash. Many diesels start a speed-limit countdown for SCR faults, so get it in soon.
How much does it cost to fix P2202?
It depends on the cause. The likely repairs for P2202 range from about $400 to $1,000 at an independent shop in the US, plus a diagnostic fee of roughly $100-$200. These are rough estimates; dealer prices and some vehicles run higher.
What is the most common cause of P2202?
The most common causes are: open in the 5 V reference wire; signal wire shorted to ground; unplugged or corroded connector.