Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Nitrogen Oxides (NOx) Modules
There are 2 NOx modules for the exhaust system. The nitrogen oxides bank 1, sensor 1 (NOx11) module is located on the right hand frame rail upstream of the selective catalytic reduction (SCR) catalyst. The nitrogen oxides bank 1, sensor 2 (NOx12) module is located on the right hand frame rail downstream of the SCR catalyst.
The NOx modules monitor the NOx sensors and control the NOx sensors heater element. The NOx modules communicate with the PCM through the controller area network (CAN) to report NOx concentrations, oxygen (O2 ) concentrations, and NOx sensor system concerns.
The NOx module consists of a microprocessor, RAM, ROM, EEPROM, heater driver, and temperature sensor. The EEPROM stores the module calibration. The heater driver supplies a pulse width modulated (PWM) voltage to the heater portion of the sensor to maintain operational temperature. The microprocessor processes all of the inputs from the sensor and communicates the information to the PCM. The temperature sensor in the module is used for compensating the temperature dependency of circuit components and for NOx module and NOx sensor rationality checks.
On some vehicles, the NOx module and the NOx sensor are an assembly.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.