OBD NH3 Sensor Heater Circuit Performance
What it means
P24E9 stands for NH3 Sensor Heater Circuit Performance. P24E9 is a P code, so the fault sits in the engine, transmission and emissions systems. For P24E9, the second digit places it in auxiliary emission controls. For P24E9, work through the cause list below, cheapest checks first.
Where it lives
For P24E9, the description names the sensor as the part involved.
What to check first
For P24E9, read the stored codes from every module, not just the engine, because related codes often name the same fault more precisely.
Check these first
- P24E9: Carbon buildup or blockage in the EGR, EVAP, or air injection system
- P24E9: Failed solenoid, valve, or pump in the auxiliary emissions circuit
- P24E9: Wiring, connector, or fuse fault for the emission component
- P24E9: Small leaks in vacuum or EVAP lines
- P24E9: Failing catalytic converter or oxygen sensor reporting incorrectly
What to do next
P24E9 reports from the auxiliary emission controls system. These steps cover P24E9 in general, and the exact cause on your vehicle can differ from the cause named above.
- P24E9: Read related codes and freeze frame with an OBD-II scanner
- P24E9: Inspect hoses, valves, and solenoids for leaks, cracks, or carbon buildup
- P24E9: Smoke test the EVAP or intake system if a leak is suspected
- P24E9: Command components on/off with a scan tool and watch them respond
- P24E9: Clean or replace the blocked or failed component
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Updated
Generic SAE J2012 definition. Last updated 2026-08-30.