⚡ AUTO CODE FIX
🔍
EmissionsModerate✅ DIY Friendly

P0400

Exhaust Gas Recirculation Flow Malfunction

General EGR flow fault. The EGR system recirculates exhaust gases to reduce NOx emissions.

SeverityModerate
CategoryEmissions
Est. Repair Cost$50–$400
Code TypePowertrain
DIY RepairYes

⚡ Common Causes

⚠️ Symptoms

✅ How to Fix — Step by Step

  • Step 1:Clean EGR valve with throttle body cleaner
  • Step 2:Test EGR valve operation
  • Step 3:Clean EGR passages
  • Step 4:Replace EGR valve if stuck
💡 Pro Tip: Carbon-clogged EGR valves respond well to cleaning — disassemble and clean before replacing.

Repair Cost Estimate

Full Repair Estimate
$50–$400
DIY Possible?
YES
Severity
Moderate

Frequently Asked Questions

What does OBD2 code P0400 mean?+
P0400 stands for Exhaust Gas Recirculation Flow Malfunction. General EGR flow fault. The EGR system recirculates exhaust gases to reduce NOx emissions.
What causes code P0400?+
Clogged EGR valve with carbon; Faulty EGR valve; Blocked EGR passages; EGR temperature sensor fault
How do I fix code P0400?+
Clean EGR valve with throttle body cleaner; Test EGR valve operation; Clean EGR passages; Replace EGR valve if stuck
How much does it cost to fix P0400?+
Estimated repair cost for P0400 is $50–$400.
Is P0400 DIY-friendly?+
Yes — P0400 is generally DIY-friendly with basic tools.

AI Diagnosis

Related Codes

P0130O2 Sensor Circuit Malfunction Bank 1 Sensor 1
ModerateDIY
P0131O2 Sensor Circuit Low Voltage Bank 1 Sensor 1
ModerateDIY
P0132O2 Sensor Circuit High Voltage Bank 1 Sensor 1
ModerateDIY
P0133O2 Sensor Circuit Slow Response Bank 1 Sensor 1
ModerateDIY
P0134O2 Sensor Circuit No Activity Bank 1 Sensor 1
ModerateDIY
P0151O2 Sensor Circuit Low Voltage Bank 2 Sensor 1
ModerateDIY