P0402
Exhaust Gas Recirculation Flow Excessive Detected
EGR flow is higher than expected when the valve should be closed, or higher than commanded when partially open. Typically a valve that has stuck open due to carbon, causing rough idle and stalling.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- EGR valve stuck openCommon
- Valve seat eroded — does not sealPossible
Parts involved
- EGR Valve
P0402 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.