The EGR system routes a small amount of exhaust gas back into the intake to lower combustion temperatures and reduce NOx emissions. EGR codes usually come from carbon buildup clogging the valve or the passages, or a failed solenoid/sensor. You may feel a slight loss of power or rough idle.
Causes are listed roughly in order of how often they're seen on Canadian independent-shop tickets. Always confirm with a scan-tool freeze-frame and a circuit/sensor check before replacing parts.
