EGR valve

P0400 EGR valve not working properly

By: Diagno editorial team · Updated: 2026-10-15

P0400 means: EGR valve not working properly. The EGR valve sends part of the exhaust gas back into the engine. OK to drive, but have it checked soon. The repair usually costs about €80–600 in Estonia. The most common cause: EGR valve clogged with soot.

Is it safe to drive?OK to driveOK to drive, but have it checked soon.

Typical repair cost€80–600parts and labour in Estonia

What it means

The EGR valve sends part of the exhaust gas back into the engine. The engine computer thinks too little is flowing. Usually the valve or passage is clogged with soot.

What could be wrong

1EGR valve clogged with soot
2EGR passages blocked
3EGR cooler blocked
4Valve actuator has failed

What you can check yourself

If you mostly do short trips, take a longer motorway drive. If the code stays, the EGR needs cleaning. You can check the simple things yourself, but the repair is best done in a workshop.

How we fix it

We check how the valve works with a diagnostic tool
We clean the valve and passages
We replace the valve if cleaning isn't enough

Standard SAE description: Exhaust Gas Recirculation Flow Malfunction

This code usually comes with: Check engine lightSee what the light means →

Want a definite answer?

Bring the car to our workshop in Estonia for diagnostics. We read the fault codes, test the sensors and tell you what is wrong. Repair price depends on the work involved, generally €45 per hour.

Book a diagnostic check

Questions

What does fault code P0400 mean?

EGR valve not working properly. The EGR valve sends part of the exhaust gas back into the engine. The engine computer thinks too little is flowing. Usually the valve or passage is clogged with soot.

Can I drive with code P0400?

OK to drive, but have it checked soon.

How much does it cost to fix P0400?

Roughly €80–600 in Estonia. The price depends on exactly what has failed and on the car.

How is P0400 fixed?

We check how the valve works with a diagnostic tool. We clean the valve and passages. We replace the valve if cleaning isn't enough.

Based on AI combined with our hands-on workshop experience and knowledge. This information is general and prices are approximate (Estonian workshop rates). The same code can mean different things on different cars. Only an inspection of the car gives a definite answer.