P0401: Exhaust Gas Recirculation Flow Insufficient
97 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), 2011-2023 Nissan Leaf, and 2004-2015 Toyota Prius, plus 94 other vehicles, with repair costs ranging from $20 to $15,000.
Common Causes
Typical Repair Cost
Based on 118 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 (97)
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
DPFE Sensor / EGR Failure Setting P0401 and Companion P0171/P0174 Lean Codes
DPFE / EGR Pressure Sensor Failure — Rough Idle, Stalling, and P0401 (2-Valve Triton)
Intake Manifold Gasket and EGR Tube Failures (Vacuum/Coolant Leaks)
EGR flow fault / check engine light from failed DPFE sensor (P0401 / P1401)
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
Premature Engine Mount Failure Causing Vibration
Hybrid Inverter/Power Control Unit (PCU) Cooling System Failure
Hybrid Power Loss While Driving
Type R Limited Slip Differential Noise and Chattering
Soft Top Tears and Rips
Sunroof/Hatch Water Leaks (SC Models)
Tailgate/Liftgate Hinge and Lift Support Problems
EGR Port Carbon Clogging — P0401/P0402 Check-Engine Light and Rough Idle (TSB 99-085)
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
Rear Brake Noise and Premature Wear
Mass Airflow (MAF) Sensor Failure
A/C Condenser Leak
EGR Valve and Passage Carbon Buildup
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 insufficient-flow code (P0401) with rough idle / check-engine light
OM656 Diesel Emissions System Clogging (EGR/DPF/AdBlue SCR) and Limp Mode
EGR Valve and EGR Cooler Carbon Clogging (Limp Mode, P0400-Series Codes)
OM651 Diesel DPF and EGR Clogging (B180 CDI / B200 CDI)
Diesel EGR/DPF Clogging & AdBlue (SCR) System Faults (OM651/OM654)
Battery Pack Capacity Degradation
Concentric Slave Cylinder (CSC) Failure
Coolant Leak from Thermostat Housing (VQ35DE)
A/C Compressor Failure
Astra K 1.6 CDTI "Whisper Diesel" EGR Cooler Internal Leak and DPF Clogging
Zafira Tourer 1.6 CDTI EGR Cooler Failure
Insignia A 2.0 CDTI EGR Cooler Crack (Coolant Loss into Intake)
Diesel EGR valve and DPF clogging on short-journey use
1.6 CDTI EGR Valve & Cooler Carbon Clogging (P0401)
Astra J 1.7 CDTI EGR Valve Clogging
1.6 TDI (EA189) Dieselgate Recall and Post-Fix EGR/DPF Failures
1.6 TDI (EA189) diesel injector and EGR valve failures
2.0 TDI (EA189) EGR cooler cracking and DPF blockage
2.0 TDI EGR System and DPF Failure
2.0 TDI EGR Cooler Failure (Dieselgate-Era Engines)
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
EGR Valve and VSV Carbon Clogging Causing P0401 Insufficient Flow
P0401 EGR Insufficient Flow — Clogged EGR Passages (5VZ-FE)
EA888 Plastic 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
EGR valve failure and limp mode after EA189 "Dieselgate" emissions recall fix
EGR valve sticking/clogging causing insufficient-flow fault and limp mode
2.0 TDI diesel particulate filter (DPF) and EGR clogging
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
Aisin TF-80SC 8-Speed Transmission Shudder and Harsh Shifting
Sensus Infotainment System Lag, Crashes, and Black Screen
Four-Corner Air Suspension Compressor and Strut Failure
Diesel EGR Cooler and Valve Clogging Causing Limp Mode (P0401)
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 97 vehicle models from 25 manufacturers: BMW, Chrysler, Citroen, Dodge, Ford, GMC, Honda, Hyundai, Jeep, Kia, Land Rover, Mazda, Mercedes-Benz, Mitsubishi, Nissan, Opel, Peugeot, RAM, SEAT, 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
- 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
- RecallNHTSA Recall 24V267 / Ford Recall 24S24 - BCM/PCM Software Update
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.