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VAG 16784Exhaust gas recirculation (EGR) flow
16784 is the VW Group 5-digit number VCDS (and older VAG-COM versions) shows for P0400. P0400 means “Exhaust gas recirculation (EGR) flow”. It's a generic powertrain code (auxiliary emission controls), so it means the same on every make, including VW, Škoda, Audi, SEAT and Cupra.
- Fix soon
- SystemEmissions
- TypeGeneric (same on all makes)
- VCDS number16784
How urgent is it?
Worth fixing soon; usually drivable meanwhile, but watch for symptoms.
Which system and module
Scanline files it under Emissions. The first letter, P, means powertrain (engine, transmission, emissions).
Usually stored by the engine control unit (VCDS address 01, Engine).
What usually causes it
- EGR valve
- EGR cooler
- passages
Typical causes are a starting point, not a diagnosis of your car.
What a shop would usually check first
The EGR valve and passages for carbon build-up, and the EGR cooler.
Related codes
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Open ScanlineScanline explains fault codes; it isn't a repair authority. This page explains what the code means; it can't tell you what is wrong with your car. Ross-Tech's wiki has their own notes on VW Group faults.