P24EC
NH3 Sensor Supply Voltage Circuit High
The NH3 slip sensor supply voltage rises above the upper limit. Either the supply is shorted to battery voltage or an internal regulator in the dosing module has failed open. The sensor electronics may be damaged if the condition persists, so the ECM disables the input.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Supply line shorted to battery voltageCommon
- Failed voltage regulator in the dosing modulePossible
- Connector pins corroded - high contact resistanceLess likely
Parts involved
- Nh3 Sensor
- Supply Wiring
- Dosing Module
P24EC 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.