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That's going to be an EGR code. More than likely your EGR valve is either clogged with carbon buildup or it stopped working altogether.
Another culprit could be the EGR solonoid but most likely its the valve itself.
Mass Air Flow sensor just measures incoming air flow at a predetermined rpm/load. The computer is saying the flow measurement is not correct. This can be caused by mechanical faults within the engine like a bad valve seat or timing chain but would generally be accompanied by backfires through the intake. Usually its caused by a vacume leak between the sensor and the intake valve,like the intake manifold,loose intake pipe clamps, broken vacume lines,a leaking vacume brake booster [it will hiss loud when you apply the brake],bad spark plugs/wires, a clogged catalytic converter, stuck open egr valve or pcv valve,bad oxygen sensor or even a very clogged air filter. I know there is a lot listed but the MAF or MAP sensors show general flow through the engine that can be affected by several things. A vacume tester from your local auto parts store is about 30bucks and usually has instructions how to test for vac. leaks within the engine also to determine a if thers is bad valve seat or clogged exhaust.
Hello, Your best move now is to go to an autoparts store and get your computer cleared. This is done free at Autozone or Oreillys after they scan your car. Your old trouble code will show for quite a few Start-ups unless you have the computer cleared. You may have fixed your problem and don't know it yet.
Code 401 is an EGR flow problem. You have repaired several things which can cause it. The remaining possibilities would be a control solenoid for Vacuum to the EGR, and if equipped, a Backpressure pipe from an exhaust manifold or Catalytic converter. The trouble Codes for many Manufacturers are the same and they pinpoint the same bad parts.
I hope you just need to clear the computer and that my solution is very helpful to you.
EGR stands for Exhaust Gas Recirculation, which basically sends some of
the exhaust back into the engine cylinder again. Your error means that
there isn't enough of the exhaust gas making it back to the intake
The first thing I'd check is the tubes coming off of the EGR
valve to make sure they aren't clogged or broken. Then I'd check the
EGR valve itself and the throttle body. The problem is usually:
1.) Carbon buildup causing a clogging.
2.) Broken hoses.
3.) Broken Valve.
To check the EGR system operation bring the Engine up to operating temperature and, with the transmission in neutral (parking brake set and tires blocked to prevent movement), allow it to idle. Open the throttle so the engine speed is between 2000 and 4000 rpm and then allow it to close. The EGR valve stem should move if the control system is working properly. The test should be repeated several times. Movement of the stem indicates the control system is functioning correctly. If the EGR valve stem does not move. Check the vacuum signal to the EGR valve. Remove the hose from the valve, place your finger over the end of the hose and perform the procedure again. If no vacuum is present at the end of the hose check the hose connections to make sure they are not leaking or clogged, then check the EGR control solenoid. also check all hoses for cracks, kinks, broken sections and proper connections. I hope this will help you.
make sure egr passage way from valve to intake not clogged and make sure exhaust to egr supply is present and make sure if valve is vacuum operated that senser is ok and vacuum supply correct if electial egr senser then intake probably clogged sense code 401 is insuffence egr flow
Check the timing belt which might be broken--if so, there will be severe valve and piston damage to cope with. If the belt is intact, then you may have a bad crankshaft or camshaft sensor, either of which will cause loss of ignition and injector action. Good luck!
The egr valve has insufficient flow, take it off, or have it taken off, and clean the under side of it, there might be a port clogged, or the diaphram inside is leaking, in which case the valve will need replacing.
That would be exactly what I would look for... When the catalytic honeycombs become blocked, it causes a build-up of exhaust pressure... and this restriction in the exhaust will also have a very definite effect on engine performance: The typical symptoms are an engine that initially seems to running okay, but slowly loses power.. in severe cases it will lose power to the point the engine stalls and will not restart until the pressure build up bleeds off.
Good luck with the problem --- it sounds like you are on the right track. And don't forget to rate my advice: your approval is my "paycheck"!