Q: CODE;EGR LOW FLOW

Typically, on this engine there will be a blockage, consisting of hard packed carbon, in the passageway in the plenum. It can be very difficult to clean out those passageways on the vehicle without removing the aluminum plenum for a thorough inspection. I have also seen the valve fail sequentially so it would not surprise me if the "newer" valve tests bad. You can test it on or off the vehicle. If you actuate (open) the valve at idle and there is no engine stumbling, that means the valve is not functional and/or the passageway through the plenum is blocked. I would first test the valve (replace as necessary) and thoroughly clean the plenum and see if that resolves it. Other causes of Diagnostic Trouble Code P0401 include a vacuum restriction to the MAP sensor, excessive back pressure in the exhaust system, any cause of low engine vacuum, and exhaust system leaks. If you want this issued diagnosed by a certified mechanic, dispatched by YourMechanic right to your location, please request an EGR system diagnostic/valve inspection and the responding certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.