NOx Sensor Circuit Range/Performance Problem
The NOx sensor is reading outside the expected range.
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What it means (plain English)
The NOx sensor measures nitrogen oxide levels in the exhaust. If it's not working right, it can send bad signals indicating too little or too much NOx is present, which affects engine performance and emissions.
What the computer is actually seeing
The engine control unit (ECU) expects to see a voltage signal from the NOx sensor that usually ranges between 0.5V to 4.5V when monitoring NOx levels. If it receives values that are too low or high, it registers a fault code.
What a healthy reading looks like
Normally, the NOx sensor output should vary between 0.5V (low NOx) to 4.5V (high NOx).
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. Check the wiring and connectors to the NOx sensor for damage or corrosion. Look for frayed wires or loose connections. If found, repair and retest.
- 22. Inspect the exhaust system for leaks near the NOx sensor. Seal any leaks and retest.
- 33. Measure the voltage output of the NOx sensor with a multimeter. You should see a signal between 0.5V and 4.5V during operation. If the voltage reads outside this range, proceed to the next step.
- 44. Replace the NOx sensor if defects have been confirmed in the previous steps and verify it does not return with a proper calibration of the engine management system.
Common causes
- Faulty NOx sensor
- Wiring harness damage or corrosion
- Exhaust leaks affecting sensor readings
- Contamination in the exhaust system
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code active?
Moderate severity means you can drive, but fix it soon. Prolonged driving may lead to higher emissions and potential engine performance issues.
Will this code come back after reset?
If the underlying issue isn’t fixed, yes, it will likely return after clearing the code.
Why is this code often paired with SPN 1970?
Both codes relate to NOx sensor monitoring; they indicate similar issues or failures in the NOx monitoring system.
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