Nitrogen Oxide (NOx) Sensor Circuit High
Indicates a high signal from the NOx sensor circuit.
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What it means (plain English)
The NOx sensor is sending a voltage reading that is above the expected range, which usually means something is wrong with the sensor or its wiring.
What the computer is actually seeing
The engine control unit (ECU) monitors the NOx sensor voltage, which should typically be between 0.1V to 5.0V depending on conditions. A reading above 5.0V triggers the fault.
What a healthy reading looks like
NOx sensor voltage should be between 0.1V and 5.0V; values below or above this range may indicate a fault.
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 to the NOx sensor for damage or corrosion. If found, repair or replace as necessary.
- 22. Measure the voltage at the NOx sensor connector with the engine running. It should be between 0.1V and 5.0V. If it's above 5.0V, continue to the next step.
- 33. Check the NOx sensor output by replacing it temporarily with a known good sensor. If the problem goes away, the sensor is bad. If not, consider an ECU issue.
- 44. If the wiring is intact and the sensor tests good, use a scan tool to check for any related fault codes or pending codes for further diagnosis.
Common causes
- Faulty NOx sensor
- Damaged wiring or connectors to NOx sensor
- ECU software issue
- Contamination in exhaust gases affecting sensor reading
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's drivable but you should fix it soon due to potential emissions issues.
Will the code come back after clearing it?
If the underlying issue isn't fixed, then yes, it will likely return.
Why does this code sometimes pair with other codes?
Related codes often indicate other problems like exhaust system issues that can affect the NOx readings.
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