P0401 - Exhaust Gas Recirculation Flow Insufficient Detected
Possible causes
- Harness or connectors (EGR volume control valve circuit is open or shorted.)
- EGR volume control valve stuck closed
- EGR volume control solenoid valve
- Dead (Weak) battery
- EGR passage clogged
- Exhaust gas leaks
Possible solution
- Clean EGR Valve
- Repair EGR harness or connector
- Replaced EGR volume control solenoid valve
- Replaced EGR volume control valve
That code refers to the EGR Valve(exhaust gas recirculation valve). This code usually indicates insufficient flow at the EGR valve. Some say to remove and clean the valve. I don't know how reliable this is. You will need to check for any loose connections or vacuum lines going to the valve. If all seems ok, I would recommend replacing the EGR valve with a new one. After replacement, be sure to have the code cleared with a scanner.
Actually, cleaning is a very cost effective way to handle the situation as long as carbon has not gotten into the throttle body and caused a blockage there. Apply sucction to the EGR valve after you remove it to make sure the diaphragm is working the valve properly. The valve can be cleaned efficiently with isopropyl alcohol which easily desolves the carbon without damage to the parts. The same can be done with the positive pressure hose leading to the engine--just don't use too much, you don't want to foul the system. The alcohol will evaporate after a while.
After you clean out the valve and the positive pressure tube connecting the EGR to your engine, leave the EGR valve off. If the engine can be started and runs smoothly with the valve disconnected, you may need to have the throttle body serviced. The blockage may be inside and unreachable without complete removal.
Do NOT use a wire to clean out the throttle body. It has a special coating in it which you want to keep in tact. (Keep in mind, that there may be other issues. You have five major parts to the '98 Taurus EGR system and any one of them could cause a problem: EGR valve, positive pressure hose (from engine), vacuum lines, timer delay/vacuum control switch, the regulator module (not on all models) and the exhaust temperature sensor. This is according to the Ford mechanic I spoke with, but I may have the wrong name for the regulator module which is separate from the timer delay switch.)
I wish you the best!
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