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I am stumped, I have replaced the EGR valve, the vacum modulator and still get a check engine light on, any thoughts or suggestions? I keep getting code P0401.

I had the guy at Checker Auto Parts test the VSV and it read 1 ohm only, when Haynes manual says between 37-44 Ohms in normal. Could that be possibly that low? We both looked at each other not sure. He even got a new meter and it read the same. I don't know maybe he didn't know what was up?

Oh yeah, first I replaced the O2 sensor on the front as the first diagnostic said Front Left Bank O2 sensor, now like I mentioned I keep getting code P0401. The O2 sensor code seems to have been resolved.

Any help would be appreciated. In parts alone I am over $300 in the hole and probably could take some back as they look new if not needed? The car runs good with the check engine light on, but it will be difficult to sell a year from now unless fixed. Thanks for your help.

Dan M.

21 Posts
Hey Dan,

I feel your pain, I've been chasing this same issue for months now without any luck. I have replaced almost everything that was either faulty or looked warn such a vacuum hoses and still have the same issue.

Before replacing anything else did you or your mechanic verify each component that showed a failure? Sometimes one sensor may cause another to read bad and throw a code. Listed below are some common issues related to the P0401 code.
  • Restriction in the EGR passages, usually caused by carbon buildup
  • Lack of a proper vacuum signal to the EGR Valve from EGR Vacuum Solenoid
  • EGR Vacuum Modulator is defective
  • EGR Temperature Sensor is defective
  • EGR Valve is defective
Keep me posted and let me know how you make out, GOOD LUCK!

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