Sensor - GM (40009741)

GM part 40009741 is a NOx (Nitrogen Oxide) Sensor Assembly.

Key details:

• Type: Exhaust emissions sensor (NOx sensor)
• Function: Measures nitrogen oxide levels in the exhaust stream so the engine control module (ECM) can adjust emissions and DEF/SCR system operation
• System location: Typically mounted in the exhaust aftertreatment system (SCR catalyst area), depending on application

Important note:

• GM part 40009741 is a replacement/supersession part
• It replaces GM part 24000237 (NOx Sensor Assembly – Position 2)

Common usage: This sensor is used on GM diesel applications with SCR emissions systems, including select:

• Chevrolet Silverado HD / Sierra HD (Duramax diesel)
• GMC Sierra / Yukon HD variants (diesel-equipped)
• Other GM diesel platforms using urea (DEF) aftertreatment

Because NOx sensors are position-specific, correct fit depends on whether it’s:

• Upstream (pre-catalyst) or downstream (post-catalyst / position 2)

If you want, send your year, make, model, engine (or VIN) and I can tell you exactly which position and whether 40009741 is the correct one for your truck.