P0401 means the EGR (Exhaust Gas Recirculation) valve is not flowing enough exhaust gas back into the intake manifold. The EGR system reduces nitrogen oxide emissions by diluting the intake charge with inert exhaust gas. Carbon buildup is the most common cause, especially on diesel engines.
DTC/P0401·Honda
P0401 on Honda: Causes, Symptoms and Fix Cost
Quick Answer
Low SeveritySafe to drive (short-term)Honda
P0401 on a Honda means the EGR (Exhaust Gas Recirculation) valve is not flowing enough exhaust gas back into the intake manifold. The EGR system reduces nitrogen oxide emissions by diluting the intake charge with inert exhaust gas. Carbon buildup is the most common cause, especially on diesel engines.
Repair cost on Honda€7 - €495
What does P0401 mean on a Honda?
Honda Civic
2006-2024Honda Civics with the R18A engine use a relatively simple EGR setup that rarely fails. The 1.5T (2016+) uses a different emissions strategy and may not have a traditional EGR valve on all markets. If P0401 appears on a 1.5T, verify the EGR system is present for your specific market variant.
What causes P0401 on a Honda?
Beyond the generic causes listed on the main P0401 page, these are the Honda-specific patterns we see most often:
Honda CivicStandard carbon buildup on R18A at high mileage
Honda CivicMarket-specific EGR configuration on 1.5T (verify presence)
How to diagnose P0401 on a Honda with OBD2
Follow these steps to pinpoint the root cause of P0401:
- Check if the EGR valve is mechanically stuck by removing it and inspecting for heavy carbon deposits
- Test EGR valve operation: apply vacuum (vacuum-operated) or command open with scan tool (electronic). The valve should open and the engine should stumble or stall
- If the valve opens correctly, check the EGR passages in the intake manifold for carbon blockage
- On DPFE-equipped vehicles (many Fords), test the DPFE sensor and its hoses for cracks or blockage
- On diesel engines, inspect the EGR cooler for blockage or internal leaks
- Check vacuum supply hoses on vacuum-operated EGR systems for cracks or disconnection
How much does P0401 cost to fix on a Honda? (EUR)
Estimated repair costs on a Honda (Honda parts and labour typically run 10% below the average for this code).
Prices estimated as of May 2026. Costs vary by region, vehicle, and shop.
Related codes that often appear with P0401 on Honda
These codes commonly cluster with P0401 on Honda vehicles:
FAQ: P0401 on Honda
Can I drive with P0401?
Yes. The EGR system is emissions-related only. You may notice slightly rougher idle, and the car will fail emissions testing. Some vehicles limit power with EGR faults.
Can I clean the EGR valve instead of replacing?
Yes, try cleaning first. Carbon buildup is the most common cause. Removal, soaking in EGR cleaner, and manual cleaning works on many valves. If the valve mechanism is damaged, replacement is needed.
Why do diesel engines get P0401 more often?
Diesel combustion produces much more soot. This carbon passes through the EGR system and clogs the valve and passages faster. Diesel EGR may need cleaning every 60,000-100,000 km.
Is EGR delete legal?
No, in most countries. It increases nitrogen oxide emissions, triggers permanent check engine lights, fails emissions tests, and can result in vehicle deregistration in some EU countries.
Looking for the full P0401 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0401 guideSkanyx · Honda
Diagnosing P0401 on your Honda?
Connect any Bluetooth OBD2 adapter, scan for codes, and get AI-powered diagnostics with severity ratings and repair cost estimates.
Download Skanyx