P24E7NH3 Sensor Heater Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P24E7 points to a heater circuit of the NH3 sensor that reads too low: the feedback voltage stays near ground, or the current is far below what the heater should draw. Most often the heater feed is shorted to ground, which can also blow the fuse or switch off the driver to protect it; a heater whose resistance has risen sharply gives a similar picture. The probe then heats slowly or not at all, and the ammonia value stays unavailable. No manufacturer publishes P24E7 with thresholds. CARB's heavy-duty OBD rule demands that heater current or voltage drop outside the maker's limits be flagged. The open-circuit fault is P24E6, the high fault P24E8 and heating performance P24E9.
- What you may notice
- Check engine light on
- Ammonia value missing or delayed after start
- Likely causes
- LikelyHeater supply line shorted to ground
- PossibleHeater element with strongly increased resistance
- RareBlown fuse in the heater supply
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €100 – €1,400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.