OBD NH3 Sensor Circuit Low
What it means
P24E3 stands for NH3 Sensor Circuit Low. P24E3 is a P code, so the fault sits in the engine, transmission and emissions systems. For P24E3, the second digit places it in auxiliary emission controls. For P24E3, work through the cause list below, cheapest checks first.
Where it lives
For P24E3, the circuit described runs through the sensor. The description of P24E3 reports a fault at the sensor.
What to check first
For P24E3, check the wiring and connector on this circuit first, since a broken terminal gives the same reading as a failed part.
Check these first
- P24E3: Carbon buildup or blockage in the EGR, EVAP, or air injection system
- P24E3: Failed solenoid, valve, or pump in the auxiliary emissions circuit
- P24E3: Wiring, connector, or fuse fault for the emission component
- P24E3: Small leaks in vacuum or EVAP lines
- P24E3: Failing catalytic converter or oxygen sensor reporting incorrectly
What to do next
P24E3 is a fault in the auxiliary emission controls system. The steps below are general, so what actually failed on your vehicle may not be what P24E3 names.
- P24E3: Read related codes and freeze frame with an OBD-II scanner
- P24E3: Inspect hoses, valves, and solenoids for leaks, cracks, or carbon buildup
- P24E3: Smoke test the EVAP or intake system if a leak is suspected
- P24E3: Command components on/off with a scan tool and watch them respond
- P24E3: Clean or replace the blocked or failed component
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Updated
Generic SAE J2012 definition. Last updated 2026-08-30.