P24E5
NH3 Sensor Circuit Intermittent/Erratic
What it means
The ammonia (NH3) slip sensor downstream of the SCR catalyst delivers an intermittent or erratic signal. The ECM expects a smooth voltage proportional to ammonia concentration in the tailpipe — sudden jumps, dropouts or noise mean the wiring, connector or sensing element is failing. Used to close-loop the AdBlue/DEF dosing strategy.
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
Corroded or loose sensor connector
highOne of the most commonly reported causes for this code — check this first.
Chafed or vibrating harness near the exhaust
mediumA plausible cause — test and verify before replacing parts.
Aged ceramic sensor element drifting under heat cycles
mediumA plausible cause — test and verify before replacing parts.
Related help
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