P0401: Exhaust Gas Recirculation Flow Insufficient
86 vehicles · 25 makes · $20-$15,000 repair
Most Reported On
P0401 is an OBD-II diagnostic trouble code meaning “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. This code is most commonly reported on 2007-2021 Toyota Tundra (1794 Edition, Base, Limited, Platinum, SR, SR5, TRD Pro), 2004-2015 Toyota Prius, and 2011-2023 Nissan Leaf, plus 83 other vehicles, with repair costs ranging from $20 to $15,000.
Common Causes
Typical Repair Cost
Based on 100 documented vehicle-specific issues. Actual cost depends on root cause and vehicle.
Diagnostic Tools
To diagnose P0401, you'll need an OBD-II scanner. Here are our recommendations at every price point.
ANCEL AD310 Classic OBD-II Scanner
by ANCEL
A simple, affordable code reader that reads and clears check engine codes. Great for quick diagnostics on any OBD-II vehicle (1996+).
- Read & clear engine codes
- View freeze frame data
- I/M readiness status
- No batteries or app needed
BlueDriver Pro Bluetooth Scanner
by BlueDriver
Bluetooth OBD-II scanner with a free companion app. Provides enhanced diagnostics, smog readiness, and repair reports sourced from a database of verified fixes.
- Enhanced diagnostics (ABS, SRS, transmission)
- Repair Reports with verified fixes
- Smog check readiness
- Free app (iOS & Android)
LAUNCH CRP123X OBD-II Scanner
by LAUNCH
A professional-grade handheld scanner that reads all four major systems (engine, transmission, ABS, SRS) with live data streaming and graphing.
- Engine, transmission, ABS, SRS diagnostics
- Live data stream & graphing
- AutoVIN for vehicle identification
- Free lifetime updates via Wi-Fi
Autel MaxiCOM MK808S Diagnostic Tool
by Autel
Shop-level diagnostic tablet with bi-directional control, active tests, and full system coverage. Ideal for serious DIYers and small shops.
- All-system diagnostics (25+ modules)
- Bi-directional control & active tests
- Oil reset, EPB, BMS, TPMS, injector coding
- 7-inch touchscreen with Android OS
As an Amazon Associate, we earn from qualifying purchases. Prices are approximate and may vary.
Vehicles Affected (86)
6.7L Power Stroke EGR Cooler Clogging and Failure
12V Battery Drain and Loss of Drive Power - Recall 24S24 + SSM 53087
Driveshaft Carrier Bearing Failure
360-Degree / Rearview Camera System Failure
6.0L Powerstroke EGR Cooler Rupture and Coolant Leak
8L90 8-Speed Torque Converter Shudder
6T40/6T45 6-Speed Transmission Shudder and Harsh Shifts
9T65 9-Speed Transmission Harsh Shifts and Hesitation
8L45 8-Speed Transmission Torque Converter Shudder
EGR Cooler Failure and Coolant Contamination (Duramax LMM/LML)
Front Axle Disconnect Actuator and IWE Hub Failure (4WD Engagement Issues)
1.5T CVT Transmission Judder and Valve Body Failure
CVT Shudder/Judder During Acceleration
CVT Shudder/Judder During Acceleration
IMA Hybrid Battery Pack Failure and Reduced Performance
Hybrid Inverter/Power Control Unit (PCU) Cooling System Failure
Premature Engine Mount Failure Causing Vibration
Hybrid Power Loss While Driving
Type R Limited Slip Differential Noise and Chattering
Sunroof/Hatch Water Leaks (SC Models)
Soft Top Tears and Rips
Tailgate/Liftgate Hinge and Lift Support Problems
Electrical System Issues and Starter Failures
IMA Hybrid Battery Failure (All Generations)
EGR System Clogging (Lean Burn Engine)
ICCU Failure and 12V Battery Drain
Hybrid High-Voltage Battery Degradation
Headlight and Taillight Moisture Condensation
Regenerative Braking Loss and Reduced Braking Power
Onboard Charger (OBC) Failure (Niro EV)
Subframe and Underbody Rust / Corrosion
Rear Brake Caliper Seizing / Parking Brake Cable Corrosion
Rear Brake Caliper Seizing
Rear Brake Noise and Premature Wear
Mass Airflow (MAF) Sensor Failure
A/C Condenser Leak
EGR Valve and Passage Carbon Buildup
EGR Valve Carbon Buildup Causing Rough Idle and P0400 Codes
EGR Valve Carbon Buildup and Coolant Leak (SkyActiv 2.5L)
EGR Valve and Passage Carbon Buildup
Battery Pack Capacity Degradation
Concentric Slave Cylinder (CSC) Failure
Coolant Leak from Thermostat Housing (VQ35DE)
A/C Compressor Failure
Diesel EGR valve and DPF clogging on short-journey use
1.6 CDTI EGR Valve & Cooler Carbon Clogging (P0401)
Zafira Tourer 1.6 CDTI EGR Cooler Failure
Insignia A 2.0 CDTI EGR Cooler Crack (Coolant Loss into Intake)
Astra J 1.7 CDTI EGR Valve Clogging
Astra K 1.6 CDTI "Whisper Diesel" EGR Cooler Internal Leak and DPF Clogging
Cam Tower Oil Leak
Hybrid Battery Pack (HV Battery) Failure
Dashboard Cracking and Melting
Frame Rust and Corrosion
Hybrid Battery Pack Degradation and Failure
6-Speed Automatic Transmission Torque Converter Shudder
KDSS (Kinetic Dynamic Suspension System) Hydraulic Leaks
EGR Cooler Condensation and Engine Intake Carbon Buildup
EGR Cooler Cracking and Coolant Leak
EGR System Carbon Buildup Causing Rough Idle and Stalling
EA888 Plastic Water Pump and Thermostat Housing Failure
EA888 Water Pump and Thermostat Housing Failure
Water Pump/Thermostat Housing Failure
Plastic Water Pump and Thermostat Housing Leak
8-Speed Automatic Transmission Rough Shifting and Shudder
Rear Taillight Seal Water Intrusion
1.6 / 2.0 TDI (EA189) EGR Valve Failure, Worsened by the Dieselgate Emissions Fix
DPF Clogging and EGR-Induced Limp Mode (diesel)
TDI diesel DPF clogging / EGR contamination on short journeys
FAQ
What does P0401 mean?
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.
What are the most common causes of P0401?
The most common causes of P0401 are: 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. The specific cause varies by vehicle.
How much does it cost to fix P0401?
Repair costs for P0401 range from $20 to $15,000, depending on the vehicle and root cause.
Which vehicles are affected by P0401?
Au7o has documented P0401 across 86 vehicle models from 25 manufacturers: Audi, BMW, Cadillac, Chrysler, Citroen, Dodge, Ford, GMC, Honda, Hyundai, Jeep, Kia, Land Rover, Mazda, Mercedes-Benz, Nissan, Opel, Peugeot, RAM, Skoda, Subaru, Suzuki, Toyota, Volkswagen, Volvo.
Sources (12)
- article6.7L EGR Cooler Failure - PowerStrokeHelp.com
- articleSinister Diesel - 6.7L Powerstroke Most Common Issues
- media3.6L Pentastar V6 Oil Filter Housing Leak Guide - Scotts U-Save
- ForumOil Filter Housing Leak pending repair - Ram Promaster Forum
- ForumOil filter housing under intake manifold cracks leaks - Ram Promaster
- ForumReddit r/MechanicAdvice thread discussing 2012 Mazda3 rear brake caliper seizing
- NHTSANHTSA Vehicle Complaints for 2017 Honda CR-V
- ForumReddit r/MechanicAdvice thread discussing 2017 Honda CR-V CVT judder
- videoHonda CR-V 1.5T CVT Transmission Shudder Repair - EricTheCarGuy
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.