NOx Exceedence - EGR System
NOx emissions are above the legal threshold and the ECU isolates the cause to the EGR system. EGR flow is too low or absent under operating conditions where NOx reduction is required.
Affected components
- Egr valve
- Egr cooler
- Egr diff pressure sensor
Common causes
- High likelihood: EGR valve stuck closed
- High likelihood: Carbon clogged EGR passages
Possible symptoms
- Check engine light on
- Pinging or knocking under load
- Power loss and hesitation
- Possible rough idle
- Failed emissions inspection (NOx)
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
- A drive cycle may be required after repair
- Reduced-power or limp mode may occur
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.