P0406Mazda Cx-30Years: 1996 - 2026
EGR Sensor A Circuit High
Reviewed by ASE Certified Technician
What does this mean?
Code P0406 indicates a problem with the Exhaust Gas Recirculation (EGR) system. The EGR system reduces NOx emissions by recirculating a portion of exhaust gas into the intake manifold.
Disclaimer: This diagnostic code is part of the standard OBD2 system and can apply to Mazda Cx-30 models manufactured from 1996 to 2026. However, please note that the presence of this specific code depends on your vehicle's exact engine configuration, options, and production year.
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Common Causes
Stuck or faulty EGR valve
Clogged EGR passages
Damaged, chafed, or broken wiring harness
Vacuum leak in intake system
Corroded or loose electrical connector
Symptoms to Watch For
- Check Engine Light is illuminated
- Rough or unstable idle
- Engine knocking or detonation noise
- Failed emissions test
- Engine stalling or dying unexpectedly
- Significant loss of engine power