Diagnostic code P0402 Not sure what that means just wondering if anyone had experienced the same issue? Don't really notice much change while driving but I'm sure there's something going on

check your egr valve system

From the 2002 factory service manual:

The EGR system is monitored for undesired EGR flow during idle. The EGR monitor looks at the DPF EGR signal at idle and compares it to the stored signal measured during key ON and engine OFF. The test fails when the signal at idle is greater than at key ON engine OFF by a calibrated amount.

Possible causes:


EGR valve stuck open
Plugged EGR vacuum regulator solenoid vent
Plugged EGR tube
Slow responding D.P.F. EGR sensor
Damaged DPF EGR sensor
Improper vacuum hose connection
Plugged vacuum hoses
EGRVR circuit shorted to ground
Damaged EGR vacuum regulator solenoid
Damaged PCM

-Rod

The check engine light when off and i wasnt going to worry about it thinking it was fixed, well unfortunately it came back on today with the same code P0402 which says exhuast gas/recirculation flow excessive detected.

EXHAUST GAS RECIRCULATION Procedure where a small amount of exhaust gas is readmitted to combustion chamber to reduce peak combustion temperatures, thus reducing NOx. Exhaust Gas Recirculation A procedure in which inert exhaust gases are recirculated to the combustion chamber to cool combustion temperatures and reduce nitrous oxides in exhaust.
the egr valve is going to cost me $200. I have check some other options as to what it could be but no luck. Anyone experience a problem like this?

Do you have the V6 or the V8? Post #3 above lists possible causes for the code. The code doesn't necessarily state the EGR valve itself is the problem. You can check the EGR by removing it and looking in the valve portion to see if it's closing completely. You can also pull a small vacuum on it if you have a MityVac or similar and make sure it opens and closes smoothly, as well as holds a vacuum and remains open with a vacuum applied. You could also try cleaning the valve portion with STP throttle body cleaner (best stuff I've found for cutting through the carbon).

If the valve checks out, there's no point in buying a new one. At that point transition your focus to the EGR vacuum regulator and vacuum lines for that system. Other Ford products have a history of issues with the DPFE. I haven't really heard of it being such an issue on the LS though.

-Rod