P0401: Exhaust Gas Recirculation Flow Insufficient
91 vehicles · 21 makes
P0401 is an OBD-II diagnostic trouble code meaning “Exhaust Gas Recirculation Flow Insufficient.” The EGR system is not flowing enough exhaust gas back into the intake. Usually caused by carbon buildup in the EGR valve or passages. This code appears across 91 vehicle models from 21 manufacturers.
Common Causes
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 (91)
G80 Integrated Brake System Weld Defect
S63 Cooling System Component Failures - E70/F85/F95 X5 M
Coolant Expansion Tank Cracking
12V Auxiliary Battery Drain - All I01 Models
Convertible Top Hydraulic Pump & Cylinder Failure (E64/F12)
Retractable Hardtop Drain Clog & Water Intrusion - E89 Z4
Oil Leaks - Valve Cover & Oil Filter Housing - All Engines
Front Suspension Bushing & Control Arm Wear - F48 X1
Convertible Top Hydraulic Pump Failure - F83 M4 Convertible
B48 Oil Filter Housing Gasket Leak/Cracking
Premature Tire Wear (All 8 Series & M8)
xDrive Transfer Case Stress & Fluid Degradation - F97 X3 M / F98 X4 M
Integrated Brake System (IBS) Failure (All 8 Series & M8)
iDrive 8 Software Bugs - Screen Crashes, Reboots & Freezing
Rear Differential Wear & Fluid Degradation - E70/F85/F95 X5 M
IBS Brake System Recall (G06)
xDrive Transfer Case Stress & Fluid Degradation - F98 X4 M / F98 X4 M
Oil Leaks - Valve Cover & Oil Filter Housing - F48 X1
DCT Dual-Clutch Transmission Wear & Judder - F10 M5
Oil Leaks - Valve Cover & Oil Filter Housing - All Models
iDrive 8 System Crashes, Reboots & Screen Blank
Phantom Braking & False Forward Collision Warnings
Integrated Hydraulic Brake (IHB) Module Failure
IBS Brake System Recall
ZF 8HP Transmission Mechatronic Issues (All 8 Series & M8)
Charging Port & Charge Flap Actuator Failure
DCT Dual-Clutch Transmission Shudder & Clutch Wear - F82/F83 M4
DCT Dual-Clutch Transmission Shudder & Clutch Wear - F87 M2/M2C
48V Mild Hybrid Battery Issues
6.7L Power Stroke EGR Cooler Clogging and Failure
6.7L Power Stroke DEF/SCR System Failure - P207F and P20EE Codes
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
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
Soft Top Tears and Rips
Sunroof/Hatch Water Leaks (SC Models)
Tailgate/Liftgate Hinge and Lift Support Problems
Electrical System Issues and Starter Failures
EGR System Clogging (Lean Burn Engine)
IMA Hybrid Battery Failure (All Generations)
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 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
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 System Carbon Buildup Causing Rough Idle and Stalling
EGR Cooler Cracking and Coolant Leak
EGR Cooler and Valve Clogging with Carbon Deposits
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
FAQ
What does P0401 mean?
P0401 stands for "Exhaust Gas Recirculation Flow Insufficient." The EGR system is not flowing enough exhaust gas back into the intake. Usually caused by carbon buildup in the EGR valve or passages.
What are the most common causes of P0401?
The most common causes of P0401 are: Carbon buildup in EGR valve, Clogged EGR passages in intake manifold, Failed EGR valve, Faulty DPFE/EGR pressure sensor, Vacuum supply issue to EGR. The specific cause varies by vehicle.
How much does it cost to fix P0401?
Repair costs vary widely depending on the root cause and vehicle.
Which vehicles are affected by P0401?
Au7o has documented P0401 across 91 vehicle models from 21 manufacturers: Audi, BMW, Cadillac, Chrysler, Citroën, Dodge, Ford, GMC, Honda, Hyundai, Jeep, Kia, Land Rover, Mazda, Nissan, Peugeot, RAM, Subaru, Toyota, Volkswagen, Volvo.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.