What it means
The NH3 sensor circuit signal is outside its expected range or does not perform as expected. The code does not identify the sensor as the cause.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
An NH3 sensor measures ammonia in the exhaust aftertreatment system so the control module can assess emissions control. P24E2 sets when the sensor circuit signal falls outside its expected range or behaves inconsistently with system operation; exhaust or reductant conditions can also affect the reading, so the code alone does not prove the sensor has failed.
Common causes
Most likely first.
- NH3 sensor drift or failure
- Damaged sensor wiring
- Loose or corroded connector
- Exhaust or reductant conditions affecting the reading
Symptoms
- Check-engine light on
- Aftertreatment or emissions warning
- Reduced engine power
- Emissions inspection failure
How to diagnose it
- Record freeze-frame data and review live NH3 readings alongside related aftertreatment codes to see when the signal went out of range.
- Inspect the NH3 sensor connector and harness for corrosion, loose terminals, heat damage, or chafing that could distort the signal.
- Check for exhaust leaks or unusual reductant-system conditions that could affect the ammonia reading.
- Use the vehicle wiring diagram to test the NH3 signal circuit and connections against the manufacturer's specification.
- If the circuit and exhaust conditions check out, compare sensor response with the specified operating test before replacing it.
Common fixes
- Repair a loose or corroded NH3 sensor connection.
- Repair damaged wiring that is affecting the sensor signal.
- Correct an exhaust leak or reductant-system issue that is skewing the reading.
- Replace the NH3 sensor if its response remains outside specification after circuit checks.
Can I keep driving?
Driving may be possible if there are no power or severe aftertreatment warnings, but emissions control may be impaired and inspection failure is possible. If reduced power occurs, limit driving and arrange diagnosis promptly.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.