P0401

2002 FORD MUSTANG
115,000 MILES • 6 CYL • AUTOMATIC
Avatar
MSZJONES
  • MEMBER
  • 1 POST
I have a 2002 mustang, it passed smog last April...I.m selling the car and need to smog...I took it in and failed smog code P0401...Have replaced egr valve...engine light still on....help
Jan 15, 2011 at 7:31 PM
Advertisement
Avatar
BMRFIXIT
  • ✓Experienced Mechanic
  • 19,053 POSTS
P0401 EGR Flow Insufficient Detected Detailed Description
The EGR system is monitored during steady state driving conditions while the EGR is commanded on. The test fails when the signal from the DPF EGR sensor indicates that EGR flow is less than the desired minimum.

Possible causes :-
Vacuum supply.
EGR valve stuck closed.
EGR valve leaks vacuum.
EGR flow path restricted.
EGRVR circuit shorted to PWR.
VREF open to DPFEGR sensor.
DPFEGR sensor downstream hose off or plugged.
EGRVR circuit open to PCM.
VPWR open to EGRVR solenoid.
DPFEGR sensor hoses both off.
DPFEGR sensor hoses reversed.
Damaged EGR orifice tube.
Damaged EGRVR solenoid.
Damaged PCM.


Diagnostic Aids
Perform KOER self-test and look for DTC P1408 as an indication of a hard fault. If P1408 is not present, look for contamination, restrictions, leaks, and intermittents.

Image (Click to enlarge)
Attached Media
Jan 15, 2011 at 8:32 PM
🔧 Tools & Auto Repair Parts
Find automotive tools, diagnostic equipment, and replacement parts for your next repair.
Shop on Amazon →
Paid affiliate link. As an Amazon Associate, we earn from qualifying purchases.
Add a reply
Join 2CarPros for free, one of the most advanced car repair communities on the internet. From first-time drivers to seasoned mechanics, everyone is welcome to reply, share details, and get better answers. You can add a temporary image or video first; uploads are limited to 20 MB.

Ask a new question

Frequently Asked Problems for This Vehicle