Faulty NOx Sensor
Diesel Exhaust Fluid
Faulty Selective Catalyst Reduction (SCR) Catalyst
Engine Light ON (or Service Engine Soon Warning Light)
The aftertreatment system is equipped with two Nox Sensors. The upstream NOx Sensor 1/1 is located at the inlet elbow of the Diesel Exhaust Oxidation (DOC) Catalyst/Diesel Particulate Filter (DPF) and is permanently connected (via a permanent wiring harness) to the NOx Sensor 1/1 Module mounted toward the front frame rail at the rear of the right front wheel well. The downstream NOx Sensor 1/2 is located at the outlet of the Selective Catalytic Reduction (SCR) Catalyst and is permanently connected (via a permanent wiring harness) to the NOx Sensor Module 1/2 mounted along the left middle frame rail. The upstream NOx Sensor 1/1 measures the NOx concentration upstream of the Catalysts. The downstream NOx Sensor 1/2 measures the NOx concentration downstream of the Catalysts. The NOx Sensors also perform a heater strategy. The NOx Sensor module monitors the sensor temperature and operates a heater inside the NOx Sensor probe to maintain proper sensor operating temperature. The NOx Sensors are smart devices and communicate with the Powertrain Control Module (PCM) over designated Data Link circuits. The NOx Sensors perform their own internal diagnostics and report malfunctions back to the PCM. The NOx Sensors are used to monitor the efficiency of the SCR Catalyst and dosing system. The PCM will illuminate the MIL lamp immediately after the monitor runs and fails.