P0406 Exhaust Gas Recirculation Sensor A Circuit High

P0406 indicates a high input from EGR sensor A. The feedback signal for EGR position or flow is higher than expected.

Code status

Needs verification

Not yet verified against SAE J2012_202509 / J2012DA. Treat unverified rows as a lookup aid, not repair authority.

System
Emissions
Scope
iso-sae-controlled-p0
Standard
SAE J2012 / ISO 15031-6
Source
legacy-import

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not replace the EGR valve before checking the feedback circuit; a high signal can be wiring, ground, reference, or sensor related.

Useful checks before replacing parts

Related OBD-II codes

These nearby emissions entries can help compare wording and fault area. They may share the same verification status as the source database.