P24EA
NH3 Sensor Supply Voltage Circuit
The supply rail that powers the NH3 slip sensor electronics (typically 5 V or 12 V from the dosing/SCR module) is out of tolerance. Without a stable supply the sensor cannot deliver a valid ammonia reading, and the ECM disables the closed-loop SCR strategy.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Open or shorted supply wireCommon
- Failing supply rail inside the dosing modulePossible
Parts involved
- Nh3 Sensor
- Supply Wiring
- Dosing Module
P24EA is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.