P0400 on Toyota
Exhaust Gas Recirculation (EGR) Flow Malfunction
P0400 on Toyota vehicles indicates exhaust gas recirculation (egr) flow malfunction. Au7o has documented this code across 1 Toyota model — most commonly on Corolla. 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 Toyota range from $120 to $450, 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 Toyota by Model
Toyota Corolla(1 issue)
- EGR Valve and VSV Carbon Clogging Causing P0401 Insufficient Flow1994-2002
On EGR-equipped 1994-2002 Corollas the exhaust gas recirculation passages, EGR valve and the vacuum switching valve (VSV) that controls it accumulate carbon over high mileage. The restricted EGR flow trips a P0401 'Exhaust Gas Recirculation Flow Insufficient' code and illuminates the check engine light, and is a frequent smog-check failure. Owners commonly find the EGR tube/port under the intake caked with carbon, or a stuck/faulty VSV solenoid, rather than a failed valve itself.
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View P0400 across all makes →Frequently Asked Questions
What does P0400 mean on Toyota?▼
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 Toyota specifically, this code is documented across 1 model.
What causes P0400 on Toyota vehicles?▼
Common causes on Toyota: 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 Toyota?▼
Repair costs on Toyota range from $120 to $450, depending on the specific model and root cause.
Which Toyota models have P0400 documented?▼
Au7o has documented P0400 on 1 Toyota model: Corolla.