Component Location: The outlet NOx sensor (SPN 3226) is located downstream of the SCR (Selective Catalytic Reduction) catalyst in the aftertreatment system. Its exact position varies by platform: On Cummins ISX15/X15 systems — typically mounted in the exhaust outlet pipe after the SCR/DPF/ASC combined aftertreatment module, near the tail end of the aftertreatment housing. On Detroit DD13/DD15/DD16 systems — mounted in the exhaust outlet pipe after the SCR catalyst, toward the rear of the aftertreatment housing, closer to the tailpipe outlet. On PACCAR MX-13 systems — located after the SCR catalyst in the aftertreatment outlet pipe. In all cases, the outlet NOx sensor is the DOWNSTREAM sensor — positioned AFTER the SCR catalyst (not to be confused with the inlet/upstream NOx sensor located before the SCR). On most Class 8 trucks, the aftertreatment system is mounted on the vehicle frame rail or directly on the engine/exhaust outlet, and the sensor will be accessible from the driver side or passenger side depending on chassis configuration. NOTE: The existing component_location entry describing placement '12–18 inches after turbo outlet' is more consistent with an INLET NOx sensor location — the outlet sensor is at the far downstream end of the SCR system. Verify sensor position using OEM service documentation for the specific engine and chassis. Based on: OEM service manual descriptions, aftertreatment system architecture documentation for Cummins, Detroit, and PACCAR platforms.