My friends 02 v6 stang failed for this "P0401 - EGR Flow
: Insufficient Detected" Now is this something that happened because of his mac catback? When he goes in to get it fixed will the void his warrenty? Is it something we car fix, if so where is it located and what do we do thank you
Check the connections of the EGR system, all vacuum hoses, is it connected to the headers, no leaks, and is the valve working correctly. Couldn't say howto test the valve, but those are the causes of an insufficient EGR flow.
A common cause of this is the PDFE sensor, it's easy to get to and replace and costs around 30 bucks from the dealer. But before going out and getting one, you can test the egr valve by running the car at idle and connecting a live vaccuum line up to the valve. If the engine slows way down or stalls, then the mechanics of the egr system are working fine. My g/f's 2001 v6 had this problem when she got it. I just replaced the sensor and cleared the code and it fixed the problem! It's a small flat sensor located near the egr valve with 2 lines going into it. Helps to put a little soapy water on the hoses to get it to slide out easier. There's a link in the forums here somewhere with pictures of it. I'd be willing to bet a buck that this will fix the problem! Much luck on it!