Hello - New here to the forum and to Hyundai's. Any help is greatly appreciated. Here is my issue: I bought a 2004 XG350L the other day and I needed to get it , it's state inspection. I"m 99.98% sure the check engine light was not on when I pulled into Jiffy Lube to get the inspection. But it failed while there for the check engine light. So my impression at that point is that Jiffy Lube did something to it, but I couldn't prove it in court and they may be totally innocent. Either way I need to get it fixed. I could take it back (Within 5 days) but I really like the car and it was super cheap. So next , I went to Auto Zone, hooked up the computer and came up with P0401: Exhaust gas recirculation (EGR) insufficient detected. Probable cause : (1) Open or short circuit condition (2) Poor electrical connection (3) Faulty EGR valve or solenoid (4) Blocked EGR valve . - Sooooo, my mechanical skills are limited but I did rebuild a 944 engine once, so I can deal with changing a EGR valve (I think ). With Google I found you guys but not a good diagram of the engine or any good info on what I should do first. Anybody have a diagram or link to one, or dealt with this problem before? Thanks again for any help. - Ed

 

I used to hate EGR on the 2.4 and the 3.5, but it is rather easy to repair..

EGR insufficient flow ---

Vacuum

EGR solenoid to apply vacuum to valve

With engine running, I WANT you to use something to pinch the grey with yellow stripe hose at the top of the throttle body, then pinch the grey with green stripe hose... 1 of these will cause engine to slow and get a rough idle about it..

If yes, the EGR valve is fine, the diaphram hold vacuum to open valve, and pasage is clear (slow down of idle and roughness, maybe stall)..

This leaves the EGR solenoid.... replace the solenoid...

Earlier models had a brown plastic valve with 2 grey-green lines on it, dont think it is on the 2004, it would be there right by the throttle body... later model had brass restrictors shoved in the tube to drop the vacuum to 7 inch..

Report back with finding, but the solenoid is common culprit.. after replace, I usually "T" in a vacuum gauge at EGR hose and go for test drive to verify solenoid is applying vacuum to line at EGR valve

 

I tried pinching both hoses, but neither had much effect on the engine's idle. I'm assuming its the EGR valve. Luckily the guy I bought it from offered to replace it for free, so I'll find out for sure later this week.

 

EGR valve is not a common problem (and a pain to remove/replace).. take and use a piece of hose to the valve and apply vacuum with mouth or pump, and verify engine stumble/rough/slowdown/stall... all I get is either the plastic tranducer (early) and solenoid that dont operate to apply vacuum to the valve' diaphram to pull valve open..

Do you have a pic of the top of your engine... the lines in particular for the EGR ?