What does fault code P0400 mean?

Exhaust Gas Recirculation (EGR) Flow Malfunction. The ECM has detected that the actual EGR system flow does not match the expected flow.

P0400

Exhaust Gas Recirculation (EGR) Flow Malfunction

Q: What are the possible causes of P0400?

EGR valve stuck or clogged (most common); EGR passage carbon buildup; EGR position sensor signal abnormal; EGR vacuum line leak; DPFE sensor failure.

Severity: Medium Emission Control Generic Code

Detailed Description

The ECM has detected that the actual EGR system flow does not match the expected flow.

Possible Causes

EGR valve stuck or clogged (most common)

EGR passage carbon buildup

EGR position sensor signal abnormal

EGR vacuum line leak

DPFE sensor failure.

Solutions & Repair Guide

Remove the EGR valve and check for severe carbon buildup; Clean the EGR valve and passages; Check if the EGR valve can open and close freely; Check vacuum line connections; Use a scan tool to monitor EGR opening and flow.

Disclaimer: The information above is for reference only and does not constitute professional repair advice. Actual causes may vary depending on vehicle make, model, year, and configuration. Always consult a qualified technician for accurate diagnosis.