Fault-Code Library · NOx sensing
P029E: NOx sensor 2 circuit range / performance
The downstream NOx sensor signal is outside the range expected by the SCR system.
Common symptoms
- •AdBlue warning
- •Engine warning light
- •Restart countdown
- •Emissions readiness failure
Likely causes
- •Failed downstream NOx sensor
- •Wiring heat damage
- •SCR dosing fault
- •Exhaust leak or temperature issue
First checks
- •Identify sensor position
- •Compare upstream and downstream NOx values
- •Check dosing, temperature, and wiring before replacing parts
Important
NOx codes can be expensive; diagnose the full SCR system before authorizing sensor replacement.
A fault code identifies a detected condition, not a failed part. Confirm manufacturer-specific subcodes and live data.
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