My 1999 Mercury Sable will not pass DEQ. Station test results- Failed with Diagnostic Code P0401.

  • 138,000 MILES
The vehicles "service engine light" came on aprox. 4 months prior to the first visit. I took vehicle through 1st time and received a Failed with a Dia. Trouble Code P0401 Exhaust Gas Recirculation Flow Insufficient Detected. I took off EGR valve off cleaned it and checked passage ways. Put it back on and went back. The second visit I got same results. So I replaced EGR and went again. The third visit same results. I then checked EGR valve soleniod with a vaccum pressure tester and 12volt charge. It appeared to work, so I replaced the EGR pressure sensor. I unhooked the battery for a few, hooked it back. The engine light went off and I drove it 20 or so miles. Drove in for fourth visit and received test results saying Unready- OBD Sensor Status Catalyst:unready Evap:unready and EGR/VVT:unready. So I drove it 10 or so more miles and the light came back on. Drove to different station for fifth visit and got the previous results of Failed code P0401. Questions are: should I replace soleniod? Why did I get Failed and then a Sensors not ready? Is there a certain procedure of drive time of resetting computer? Please help. What to do? Thanks
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have the same problem?
Thursday, October 13th, 2011 AT 9:54 PM

1 Reply

When the computer is reset, it reads not ready because everyone would reset a light and have the emissions done. There is a certain number of miles before the computer rechecks everything. If there is still a problem, the light comes back on.

As far as the EGR, make sure the intake, where it bolts on, is free of carbon. They back up in there too. As far as the EGR, did the valve open fully when tested?
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Thursday, October 13th, 2011 AT 9:58 PM

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