Basic checks
Veepeak OBDCheck BLE
A Bluetooth LE adapter for reading standard engine codes and supported live data.
View on AmazonP24ED
NH3 Sensor Calibration Memory
Moderate severity
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.
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.
Common causes
- high
New sensor installed but not coded/learned to the ECM
One of the most commonly reported causes for this code — check this first.
Typical part cost: $90-660
- medium
Corrupted calibration memory after voltage drop
A plausible cause — test and verify before replacing parts.
Typical part cost: $90-660
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First things to check
- 1Confirm the code with a scan tool and check for additional related codes.
- 2Inspect the relevant sensors, wiring, and connectors for damage or corrosion.
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Tools you may need
Already have a compatible scanner? Use it. If not, a Bluetooth OBD2 adapter can help you confirm engine codes and check supported live sensor data before replacing parts.
Regular diagnostics
vgate iCar Pro BLE 4.0
A Bluetooth LE adapter with an automatic sleep feature for routine code and sensor checks.
View on AmazonAnother option
OBDLink CX
A Bluetooth LE adapter to consider when comparing supported vehicles and diagnostic apps.
View on AmazonIllustrations shown, not product photos. Check vehicle, phone and app compatibility before buying. These adapters do not guarantee access to ABS, airbags or manufacturer-specific systems. Clearing a code does not repair the fault and can reset emissions readiness monitors.
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Related codes
See related trouble codes
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Frequently asked questions
What does P24ED mean?
P24ED means "NH3 Sensor Calibration Memory". It is a generic OBD-II code that points to a fault in the evaporative / emission control system.
What are the most common causes of P24ED?
new sensor installed but not coded/learned to the ecm; corrupted calibration memory after voltage drop; module software outdated, reflash may resolve — these are the most commonly reported causes. Verify with a proper diagnosis before replacing parts, or use the Wrenchify app for a vehicle-specific diagnosis.
Can I keep driving with this code?
The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical. Use the Wrenchify app for a full diagnosis specific to your vehicle.
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