NOx Sensor for Caterpillar C7.1 / C9.3 / C15 - Replaces 359-9172 - 24V Nitrogen Oxide Sensor

Genuine OEM NOx Sensor — Clear Your Derate Codes

Your machine is in limp mode. The dashboard is lit up with SCR system fault codes. The dealer is backordered — or wants $800. Don't wait weeks for a sensor that costs a fraction of what Cat charges.

This is the Genuine OEM NOx Sensor — the exact same sensor that Caterpillar re-boxes in a yellow box and sells as their own. Same sensor, same software calibration, same connector, same performance. The only difference is the price.

The Problem

Modern Tier 4 Final Caterpillar engines use two NOx sensors (Inlet and Outlet) to monitor the SCR aftertreatment system. These sensors fail constantly due to:

• Exhaust heat cycling: Repeated heating and cooling cracks the ceramic sensing element
• DEF contamination: Crystallized urea deposits foul the sensor tip
• Vibration: Heavy equipment vibration breaks internal solder joints
• Water intrusion: Moisture in the exhaust system corrodes the electrical connections

When a NOx sensor fails, the ECU cannot verify emissions compliance and puts the engine into Derate Mode — severely limiting power and eventually shutting the machine down entirely.

The Solution

Replace the failed sensor with this Genuine OEM unit. It's a direct plug-and-play replacement — unplug the old sensor, unthread it from the exhaust pipe, thread in the new one, and plug it in. The ECU will recognize it immediately. Clear your codes and you're back to full power.

Technical Specifications

• Cat Part Number: 359-9172 (also listed as 359-9172-02)
• Manufacturer: Original Equipment Supplier (European)
• Voltage: 24V DC
• Type: Nitrogen Oxide (NOx) Sensor
• Connector: Direct fit Cat harness — no adapters needed
• Position: Works as either Inlet (before SCR) or Outlet (after SCR)
• Condition: Brand New, Genuine OEM

Compatible Caterpillar Equipment

Excavators

• Cat 320E / 320F Excavator (C7.1 Engine)
• Cat 323E / 323F Excavator (C7.1 Engine)
• Cat 324E Excavator (C7.1 Engine)
• Cat 329E / 329F Excavator (C7.1 Engine)
• Cat 336E / 336F Excavator (C9.3 Engine)
• Cat 349E / 349F Excavator (C13 Engine)
• Cat 352F Excavator (C13 Engine)
• Cat 374F Excavator (C15 Engine)
• Cat 390F Excavator (C18 Engine)

Wheel Loaders

• Cat 950M / 962M / 966M Wheel Loader
• Cat 972M / 980M Wheel Loader

Dozers

• Cat D6T / D7E / D8T / D9T Dozer

Motor Graders

• Cat 12M / 14M / 16M Motor Grader

Articulated Trucks

• Cat 725C / 730C / 735C / 740C Articulated Truck

This is one of Caterpillar's most universal Tier 4 Final sensors. If your parts manual lists 359-9172 or 359-9172-02, this is the correct replacement regardless of machine model.

Why Buy From Trenchwell?

• Save $300+ vs Dealer: Cat dealers charge $680–$850 for this sensor. We sell the identical Genuine OEM part for $495.
• Genuine OEM Quality: This is NOT a cheap Chinese clone. Counterfeit NOx sensors fail within days and cause cascading SCR faults. This is the real OEM sensor — the same unit Cat re-boxes and sells for $800+.
• In Stock, Ships Fast: No waiting 3 weeks for Cat to ship from their warehouse. We stock these and ship immediately.
• Also Need the DEF Injector? If your SCR system has multiple fault codes, you may also need the DEF Dosing Injector. Check our companion listing for the Denoxtronic 2.2 dosing valve.

Frequently Asked Questions

Do I need to program this sensor?
No. This is a direct plug-and-play replacement. The ECU recognizes the sensor automatically. Simply clear the old fault codes after installation.

My machine has two NOx sensors. Which one do I replace?
Tier 4 Final engines use an Inlet sensor (before the SCR catalyst) and an Outlet sensor (after). Your diagnostic codes will tell you which one has failed. This sensor works in either position. If one has failed, the other is likely near end of life too — consider replacing both.

Is this the same sensor Cat sells?
Yes. Caterpillar does not manufacture NOx sensors. They purchase them from the original equipment supplier and re-box them. Our sensor is the identical OEM unit — same calibration, same connector, same performance.