30E4
Moderate30E4 — NOx Sensor Aging
Description
What It Means
Code 30E4 points to nitrogen oxide (NOx) sensor aging. The sensor's sensing element is contaminated or worn, and its performance has dropped. The NOx sensor measures nitrogen oxide concentration in the exhaust. Both the exhaust gas recirculation (EGR) and selective catalytic reduction (SCR) systems rely on that reading to work correctly.
Symptoms
Symptoms
- Check Engine Light (CEL) comes on
- Possible drop in fuel economy
Causes and fixes
Diagnosis and Repair
Step 1
Replace the NOx sensor.
Step 2
Code the new sensor with diagnostic equipment (ISTA or equivalent).
Possible secondary damage
Indirect Problems
Ignoring the fault can lead to incorrect NOx readings, which will cause improper diesel particulate filter (DPF) regeneration and eventually damage the catalytic converter.