P0401 on Audi
Exhaust Gas Recirculation Flow Insufficient
P0401 on Audi vehicles indicates exhaust gas recirculation flow insufficient. Au7o has documented this code across 1 Audi model — most commonly on A1. This code means the Exhaust Gas Recirculation (EGR) system is not flowing enough exhaust back into the engine. The EGR system recirculates a small amount of exhaust into the intake to lower combustion temperatures and reduce nitrogen oxide (NOx) emissions; the computer has determined the actual flow is below what it commanded. The most common reason is carbon buildup clogging the EGR valve or its passages. You may notice pinging/knocking, rough idle, or a check engine light, and the car will fail emissions testing. Typical repair costs on Audi range from $200 to $1,500, depending on the specific model and root cause.
Common Causes of P0401
- •Carbon buildup clogging the EGR valve or passages
- •Stuck or faulty EGR valve
- •Blocked or restricted EGR ports/tubes
- •Faulty EGR temperature or position sensor
- •Faulty DPFE/EGR pressure sensor (on applicable systems)
- •Vacuum leak or failed vacuum control (vacuum-operated EGR)
- •Wiring or connector problems at the EGR valve
P0401 on Audi by Model
Audi A1(1 issue)
- 1.6 / 2.0 TDI Diesel DPF Clogging and EGR Valve Faults2010-2018
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.
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View P0401 across all makes →Frequently Asked Questions
What does P0401 mean on Audi?▼
P0401 stands for "Exhaust Gas Recirculation Flow Insufficient." This code means the Exhaust Gas Recirculation (EGR) system is not flowing enough exhaust back into the engine. The EGR system recirculates a small amount of exhaust into the intake to lower combustion temperatures and reduce nitrogen oxide (NOx) emissions; the computer has determined the actual flow is below what it commanded. The most common reason is carbon buildup clogging the EGR valve or its passages. You may notice pinging/knocking, rough idle, or a check engine light, and the car will fail emissions testing. On Audi specifically, this code is documented across 1 model.
What causes P0401 on Audi vehicles?▼
Common causes on Audi: Carbon buildup clogging the EGR valve or passages, Stuck or faulty EGR valve, Blocked or restricted EGR ports/tubes, Faulty EGR temperature or position sensor, Faulty DPFE/EGR pressure sensor (on applicable systems). Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0401 on a Audi?▼
Repair costs on Audi range from $200 to $1,500, depending on the specific model and root cause.
Which Audi models have P0401 documented?▼
Au7o has documented P0401 on 1 Audi model: A1.