SCR NOx Sensor Circuit Low Input
There's a low voltage signal from the SCR NOx sensor.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The Selective Catalytic Reduction (SCR) system uses a NOx sensor to measure emissions; when the sensor reports low voltage, it indicates a potential problem in the circuit or the sensor itself.
What the computer is actually seeing
The Engine Control Module (ECM) is seeing a voltage below the expected range from the SCR NOx sensor, typically around 0.5V or lower when it should be showing around 1.0V or more during normal operation.
What a healthy reading looks like
Normal NOx sensor voltage should range between 0.5V and 4.5V during operation, depending on the system design and conditions.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Inspect the wiring and connectors of the NOx sensor for damage or corrosion. Are there any signs of wear?
- 22. Check the voltage at the NOx sensor connector with the key on (engine off). Is the signal within the expected range of 0.5V to 4.5V?
- 33. If voltage is low, check continuity of the wiring between the sensor and ECM. Is the wiring intact?
- 44. If wiring is good, replace the NOx sensor and clear the code. Did the code return?
- 55. If the code returns, further check exhaust system for leaks and ECM functionality.
Common causes
- Wiring issue between the NOx sensor and the ECM
- Faulty NOx sensor
- Corroded or loose connectors
- Exhaust leaks affecting sensor performance
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Yes, but emissions may be affected, and it could lead to reduced performance over time.
Will this fault code come back after clearing it?
If there's an underlying issue, such as bad wiring or a faulty sensor, it likely will.
Why does this code appear with others like P2030?
These codes often indicate related issues within the SCR system, particularly with the NOx sensor or circuit.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
Start guided diagnostic →