P24ED
- Powertrain
- Manufacturer-specific
- Emissions
Diagnose soon
Usually safe to drive short distances, but the fault will not clear itself and can worsen or fail an emissions test.
NH3 Sensor Calibration Memory
This code is in our catalogue but has not yet been through editorial review, so the guidance below is limited to what our structured data supports. We publish deeper diagnostic content only after a code has been reviewed — here is why.
The NH3 slip sensor stores its individual calibration coefficients in non-volatile memory (EEPROM/flash). The ECM cannot read valid calibration values — either checksum fails, the memory is empty after replacement, or communication with the sensor electronics is broken. Without the trim values the raw ammonia reading is unreliable.
A trouble code records what a control module measured. It does not identify which part failed. Test before replacing anything.
- Safe to drive
- Usually safe to drive short distances, but the fault will not clear itself and can worsen or fail an emissions test.
- Urgency
- Diagnose soon
- Will it pass emissions
- No
- Check engine light
- Solid
| # | Cause | How often | Component |
|---|---|---|---|
| 1 | New sensor installed but not coded/learned to the ECM | Very common | — |
| 2 | Corrupted calibration memory after voltage drop | Common | — |
| 3 | Module software outdated, reflash may resolve | Occasional | — |
Ordering reflects how often each cause is responsible in general, not a probability for your vehicle. Confirm by testing.
- Nh3 Sensor
- Sensor Eeprom
- Definition
- Generic code set (SAE J2012 / ISO 15031-6) via the OBDexopen database, dedicated to the public domain under CC0-1.0.
- Diagnostic guidance
- Written and reviewed in-house. See our editorial policy.
- Review status
- Awaiting review
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