Standard Motor Products NOX019 Diesel Nitrogen Oxide (NOx) Sensor - Downstream

The Standard Motor Products NOX019 is a diesel Nitrogen Oxide (NOx) sensor designed as a direct-fit OE replacement for the downstream position in the Selective Catalytic Reduction (SCR) exhaust emissions system.

How It Works:

NOx sensors monitor the level of nitrogen oxide being emitted by a diesel vehicle to ensure compliance with emissions regulations. The downstream NOx sensor (Sensor 2) is positioned after the SCR catalyst and measures the NOx levels exiting the SCR system. This data is reported to the ECU to verify that the SCR system — which uses Diesel Exhaust Fluid (DEF) to reduce harmful emissions — is functioning correctly. A failed downstream NOx sensor will typically trigger a check engine light and may result in reduced engine performance or limp mode.

Key Features:

• Direct-fit OE replacement — ensures proper fit, form, and function with no modifications required
• Downstream (SCR catalyst outlet) position — monitors NOx levels exiting the SCR catalyst
• Plug-and-play design — no additional programming required for installation
• High-temperature construction — built to withstand extreme exhaust system temperatures
• Manufactured to meet or exceed OE quality standards
• UPC: 033086761879

Common Failure Symptoms:

• Check engine light illumination
• SCR efficiency or DEF quality fault codes (e.g., P20EE)
• Vehicle entering reduced-power or limp mode
• Soot buildup on sensor element, ECU water intrusion, or wiring/cable damage

Installation Note: After replacing a NOx sensor, consult your vehicle's service information for any required reset or relearn procedures. If DEF-related fault codes are also present, a manual DPF regeneration may be necessary to purge ammonia from the SCR catalyst before accurate diagnostics can be performed.