2005 Hyundai Santa Fe GLS 3.5, 158000 MILES. Automatic, 2WD. EGR insufficient flow code came up. Had EGR valve and associated components replaced. Code came back. Had Mass air flow sensor replaced at technicians recommendation. Code remains. Could it be a clogged cat? Thanks.
It's not the catalytic converter.
Those Hyundai's used the MAP sensor, not the MAF sensor, to perform the EGR flow test so if your guy is suspecting a bad sensor he needs to look at the MAP sensor.
But if that isn't it then there's other things like a clogged egr port in the intake manifold, or clogged vacuum lines, clogged orifices, or clogged vacuum ports (or leaks in vacuum lines) that will keep setting that code after you replace the egr valve.
Here's what your EGR system looks like:
Since your guy replaced all the associated components he probably replaced the Vacuum Control Valve and the EGR Solenoid Valve and the #1 orifice is part of it.
#2 & #3 are inside the vacuum lines so it's possible he didn't check if those were clogged.
And the way the setup works is the EGR Solenoid Valve is always open. When the EGR Solenoid Valve is Open The EGR Valve is closed. When the computer wants to open the EGR Valve it Closes the EGR Solenoid Valve and cuts off vacuum to one of the ports on the Vacuum Control Valve. That stops the vacuum bypass and vacuum gets applied to the diaphragm on the EGR Valve and it opens.
The reason this is useful is because you can test this entire system for clogs or leaks by cutting off the vacuum to the EGR Solenoid Valve and forcing the EGR Valve to open. (assuming you have a new EGR valve that isn't sticking open)
Locate the bleed off vacuum line on the throttle body (see above diagram). It's the vacuum line with the yellow stripe between the Vacuum Control Valve and the Throttle Body ((yours may be black with a yellow stripe of just black with a yellow band around it)).
Start the car. Reach down there and pinch that vacuum line between your thumb and your forefinger and hold it. That will cut off vacuum to the EGR Solenoid Valve and if there's no clogs (or leaks) in this vacuum system the EGR Valve will open and your car will stall. (It will also tell you that the metal tube between the exhaust and the EGR Valve isn't clogged).
If it stalls then it's time to test the circuit at the EGR Solenoid Valve connector for Power (Key On) and for the pulse-width modulated Ground signal from the computer when the EGR Solenoid Valve is commanded to close (EGR valve to open)
What, exactly , is the "code" that keeps coming back? What is the code number?
