P24E7
NH3 Sensor Heater Circuit Low
What it means
The heater control circuit of the ammonia (NH3) slip sensor reads below the expected voltage range. Either the wiring is shorted to ground or the heater driver in the SCR/dosing module is stuck low. The sensor element never warms up, NH3 readings stay invalid and the SCR strategy falls back to open-loop dosing.
Is it safe to drive?
The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical.
Most likely causes
Heater control wire shorted to ground
highOne of the most commonly reported causes for this code — check this first.
Internal short across the heater element
mediumA plausible cause — test and verify before replacing parts.
Low-side driver pulled down in the control module
lowLess common, but worth ruling out after the more likely causes.
Related help
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