P0400 on Volkswagen
Exhaust Gas Recirculation (EGR) Flow Malfunction
P0400 on Volkswagen vehicles indicates exhaust gas recirculation (egr) flow malfunction. Au7o has documented this code across 1 Volkswagen model — most commonly on Jetta. P0400 is a generic powertrain code indicating the engine computer detected a problem with exhaust gas recirculation (EGR) flow — either too much, too little, or incorrect flow compared to what was commanded. The EGR system routes a small amount of exhaust back into the intake to lower combustion temperatures and reduce emissions. A fault can cause rough idle, pinging/knock, increased emissions, and failed emissions testing, though it is generally not an immediate driving hazard. Typical repair costs on Volkswagen range from $600 to $3,500, depending on the specific model and root cause.
Common Causes of P0400
- •Clogged or carbon-blocked EGR passages
- •Faulty EGR valve (stuck open or closed)
- •Faulty EGR position or DPFE/flow sensor
- •Vacuum or electrical control fault to the EGR valve
- •Blocked or cracked EGR tube
- •Wiring/connector issues
- •PCM fault (rare)
P0400 on Volkswagen by Model
Volkswagen Jetta(1 issue)
- EGR Valve Clogging and Accelerated DPF Loading After the EA189 Dieselgate Emissions Modification2009-2014
The 2009-2014 Jetta TDI ran the EA189 2.0 TDI (CBEA/CJAA) at the centre of the diesel emissions scandal. The court-approved Approved Emissions Modification - an ECU recalibration, plus hardware on some generations - brings the car into compliance largely by leaning on the exhaust gas recirculation system far harder and altering injection. Owners and independent shops have documented the aftereffect: heavier EGR duty cycles accelerate carbon fouling of the EGR valve and cooler, and the changed combustion produces more soot, so the diesel particulate filter loads and regenerates more often, shortening its service life. Symptoms are rough idle, power loss and EGR flow codes (P0401 and relatives), or a DPF that will no longer complete a regeneration. The pattern is strong enough that Volkswagen Group has been refunding or goodwilling EGR failures in some markets, while individual dealers have told owners the failures are unrelated to the fix.
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View P0400 across all makes →Frequently Asked Questions
What does P0400 mean on Volkswagen?▼
P0400 stands for "Exhaust Gas Recirculation (EGR) Flow Malfunction." P0400 is a generic powertrain code indicating the engine computer detected a problem with exhaust gas recirculation (EGR) flow — either too much, too little, or incorrect flow compared to what was commanded. The EGR system routes a small amount of exhaust back into the intake to lower combustion temperatures and reduce emissions. A fault can cause rough idle, pinging/knock, increased emissions, and failed emissions testing, though it is generally not an immediate driving hazard. On Volkswagen specifically, this code is documented across 1 model.
What causes P0400 on Volkswagen vehicles?▼
Common causes on Volkswagen: Clogged or carbon-blocked EGR passages, Faulty EGR valve (stuck open or closed), Faulty EGR position or DPFE/flow sensor, Vacuum or electrical control fault to the EGR valve, Blocked or cracked EGR tube. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0400 on a Volkswagen?▼
Repair costs on Volkswagen range from $600 to $3,500, depending on the specific model and root cause.
Which Volkswagen models have P0400 documented?▼
Au7o has documented P0400 on 1 Volkswagen model: Jetta.