P0402 on Audi: How to Diagnose & Fix
Exhaust Gas Recirculation Flow Excessive
2 Audi models · 2 documented issues · $200-$1,500 repair
P0402 on Audi by model: symptoms, diagnosis and fix
The EGR (Exhaust Gas Recirculation) valve and cooler can fail from carbon buildup, causing rough running, poor performance, and warning lights.
Common Symptoms
- Rough idle
- Loss of power
- Check engine light
- Black smoke from exhaust
- Poor throttle response
- Coolant loss (EGR cooler leak)
How to Fix
Clean or replace the EGR valve (03L131501K). Inspect the EGR cooler (03L131512AF) for leaks - coolant loss can indicate internal cooler failure. Regular intake cleaning helps prevent carbon buildup. Use quality diesel fuel. The EGR cooler removal process is documented at myturbodiesel.com for CBEA/CJAA engines. Related OEM part numbers: EGR valve 03L131501K (Pierburg, supersedes 03L131501G); EGR cooler 03L131512AF; EGR cooler valve 03L131501F; EGR pipe to cooler 03G131547H; EGR cooler temperature sensor 03L906529A; EGR vacuum solenoid (N239/N345) 1K0906283A; EGR-to-intake-manifold O-ring seal 03G131547C. Confirm fitment by engine code.
Sources for this issue (1)
The A1 is sold mainly as a town/city car, so diesel (1.6 TDI / 2.0 TDI) owners doing short, stop-start journeys never get the diesel particulate filter hot enough for passive regeneration. The DPF clogs with soot, and a faulty/sticking EGR valve accelerates this by raising soot output. Failed active regens can also dilute the engine oil with diesel. A blocked DPF triggers limp mode and is expensive to replace.
Common Symptoms
- DPF / glow-plug warning light
- Reduced power / limp mode
- Increased fuel consumption
- Rising engine oil level (fuel dilution)
- Frequent regeneration cycles
How to Fix
Take the car on a sustained motorway run (~2,000+ rpm for 15-20 minutes) to force regeneration when the warning first appears. Clean or replace a faulty EGR valve, use the correct low-ash (504/507) oil, and have the DPF force-regenerated or professionally cleaned if heavily blocked; replace the DPF if soot load is beyond recovery. Check that the oil level isn't rising from fuel dilution.
Sources for this issue (1)
P0402 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0402 mean on a Audi?
P0402 stands for "Exhaust Gas Recirculation Flow Excessive." P0402 means the Exhaust Gas Recirculation (EGR) system is flowing too much exhaust back into the intake. The EGR system intentionally routes a small amount of inert exhaust gas into the engine to lower combustion temperatures and reduce nitrogen-oxide emissions, but the flow must be metered precisely. When the PCM determines the flow is excessive — often because the EGR valve is stuck open or letting gas through when it shouldn't — it sets this code. Too much EGR can cause rough idle, stalling, hesitation, and a check engine light. On Audi it is documented across 2 models: A3, A1.
What are the most common causes of P0402?
The most common causes of P0402 are: EGR valve stuck open or not closing fully, Failed or sticking EGR valve diaphragm/solenoid, Carbon buildup holding the EGR valve open, Faulty EGR position or differential pressure (DPFE) sensor, Leaking EGR valve gasket or pintle seat, Vacuum control or solenoid fault commanding EGR open, Wiring or connector problems in the EGR control circuit. The specific cause varies by vehicle.
How much does it cost to fix P0402 on a Audi?
Published repair estimates on Audi range from $200 to $1,500 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0402 on a different make?
View P0402 across all makes →Join 700+ subscribers following Au7o for vehicle insights and updates.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.