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P0401 and P0402 Fault Diagnosis: 2000 Ford Taurus 24 Valve DOHC V6

Model: 2000 Ford Taurus Fault Code: P0401 Posted: 2006-06-12 20:41

The check engine light on my 2000 Ford Taurus with a 24-valve DOHC V6 engine has come on. After using an OBD2 scan tool, I received both P0402 (excessive EGR flow) and later P0401 (low EGR flow). I initially replaced the DPFE sensor and spark plugs (at 40,000 miles), which temporarily resolved the 'missing' condition. However, after one week, the P0401 code reappeared along with a return of engine misfiring. Replacing the spark plugs required removing the intake manifold. During reinstallation, I noticed a small gap around the entire manifold and at the top of the engine block. I'm unsure whether this is normal or if it could be contributing to the EGR flow issues—particularly since P0402 returned after the initial fix. I'm seeking advice on possible causes for these conflicting EGR-related codes, especially in relation to intake manifold sealing and EGR valve function. Any insights from owners or mechanics familiar with this model would be greatly appreciated.

Related fault codes
P0401P0402
Comments (4)
Anonymous 2006-06-12 21:10

Did you replace any gaskets or o-rings during the repair? I recommend never reusing gaskets or o-rings as they are prone to failure when reused. Also, did you replace the spark plug wires at the same time? After replacing the spark plugs and clearing the codes, what code appeared when the check engine light returned?

Anonymous 2007-10-10 15:48

I recently experienced identical EGR issues—excessive and insufficient flow—and I'm not a certified mechanic but rather a part changer. I replaced the EGR valve and all four oxygen sensors (using original Ford parts). This didn't resolve the issue. After that, I replaced the vacuum regulator solenoid and a tube-mounted sensor with part numbers F63Z-9J459-AA and 4U7Z-9J460-AA. These changes eliminated both EGR-related codes and resolved the severe idle instability that was causing the transmission to jump into gear unexpectedly. It sometimes felt like a broken motor mount. Good luck with your repair!

Anonymous 2007-10-10 22:10

Start by inspecting the EGR valve—ensure it's functioning properly. A faulty EGR valve may fail to open or close correctly, leading to improper EGR flow. If you suspect a bad valve, replace it. Also check the vacuum hose connected to the top of the EGR valve (from the EGR solenoid) for blockages or cracks.

Anonymous 2007-10-11 06:01

The original post has already been resolved—the user is now explaining what worked, not asking for help. Additionally, reviewing the timestamps shows this thread is still relevant to owners of the 2000 Ford Taurus with EGR-related issues.