P0400

Exhaust Gas Recirculation Flow Malfunction

Severity: Medium Emission Control Generic OBD-II Code Est. Repair: $150 - $450

Schedule diagnosis soon. Continued driving may worsen the issue.

What Does P0400 Mean?

General EGR flow problem.

Common Symptoms

CEL
Possible knock or rough idle

Possible Causes

Carbon
Faulty valve
Sensor or vacuum issues

How to Fix P0400 – Repair Guide

Clean EGR system
Test valve and sensors
Sponsored Partner

Upgrading Your Vehicle or Need Replacement Clearance?

Explore high-quality aftermarket auto parts, forged wheel spacers, and leveling kits.

Recommended OBD2 Scanners & Tools

To read and clear this code yourself, you need a reliable OBD2 scanner. Here are top-rated options:

BlueDriver Bluetooth Pro OBDII Scan Tool

Professional Bluetooth scanner with live data, enhanced diagnostics (ABS/SRS) and repair reports. Works with iPhone & Android. No subscription fee.

$70 - $120
Check Price on Amazon →

ANCEL AD310 Classic Enhanced OBD2 Scanner

Best-selling handheld code reader. Read & clear engine codes, live data, freeze frame. No phone required. Highly rated for beginners.

$25 - $40
Check Price on Amazon →

FIXD Bluetooth OBD2 Scanner

Simple plug-and-play sensor that explains codes in plain English via free app. Ideal for first-time users.

$35 - $60
Check Price on Amazon →

As an Amazon Associate we earn from qualifying purchases. This does not affect the price you pay.

Disclaimer: Information is for educational reference only and does not replace professional diagnosis. Actual causes and costs vary by vehicle make, model, year and condition. Always verify with a qualified technician.