System: Emissions Control · Standard: SAE J2012 generic code · Severity: Low urgency
No immediate safety risk. Monitor it and fix it at the next service, but do not ignore it indefinitely.
An EGR valve stuck open dilutes the intake charge and makes idle unstable.
Start by reading every stored and pending code, not just this one. A single fault frequently sets three or four codes at once, and the first one in the freeze-frame data is usually the cause while the rest are consequences.
The EGR system is flowing more exhaust gas than commanded. Exhaust Gas Recirculation Flow Excessive is a generic emissions control code defined by SAE J2012, so it carries the same meaning on every OBD-II vehicle.
Low urgency. No immediate safety risk. Monitor it and fix it at the next service, but do not ignore it indefinitely.
In rough order of how often they turn out to be the problem: EGR valve stuck open; Failed EGR solenoid; Faulty sensor.
P0401 Exhaust Gas Recirculation Flow InsufficientP0411 Secondary Air Injection System Incorrect FlowP0420 Catalyst System Efficiency Below Threshold (Bank 1)P0430 Catalyst System Efficiency Below Threshold (Bank 2)P0440 Evaporative Emission Control System MalfunctionP0442 Evaporative Emission Control System Leak Detected (Small Leak)Code number, system and definition follow the SAE J2012 / ISO 15031-6 generic diagnostic trouble code standard. Symptoms, causes and severity are the standard generic diagnostic logic for that fault. This page does not contain manufacturer-specific procedures, part numbers or pricing.