P24ED code meaning
NH3 Sensor Calibration Memory
Powertrain system Generic code P24xx codes Check engine light
What P24ED means
Every NH3 sensor leaves the factory with individual correction values for offset and gain stored in its own electronics. P24ED means this memory fails its integrity check, for instance a checksum mismatch or unreadable data, so the module cannot convert the raw probe signal into a trustworthy ammonia value. The fix is normally a new sensor; wiring rarely plays a part. It differs from the engine software choice in Ram bulletin 18-042-20, where 2014 Ram 3500 to 5500 cab chassis trucks receive one controller calibration with the ammonia sensor and another without it. No manufacturer documents P24ED publicly. CARB demands that heavy-duty sensors be checked for faults. P24EE covers the sensor processor.
P24ED at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P24ED
- Check engine light on
- No valid ammonia value although wiring tests pass
Common causes of P24ED
- Most likelyCalibration data in the sensor module corrupted
- Less likelyPower loss while the module was writing data
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Nh3 sensorSensor eeprom
What each part of P24ED means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 4 | Area: auxiliary emission controls (catalytic converter, EGR, EVAP). |
| ED | The exact fault in that area. |
What to do next
- Note P24ED and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P24ED
What does P24ED mean?
P24ED means "NH3 Sensor Calibration Memory". Every NH3 sensor leaves the factory with individual correction values for offset and gain stored in its own electronics. It is a generic code, so it means the same on every make.
Is it safe to drive with P24ED?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P24ED fail an emissions test?
Yes, it can. P24ED is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P24ED to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. This is a job for a workshop.
Will P24ED clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.