P0401 Insufficient EGR Flow
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P0401 Insufficient EGR Flow
Check engine light in my 1997 4Runner 2.7L has been on a couple months and its the P0401 code. I replaced the vacuum modulator and the vacuum switching valve but the light remains on. I have zero drivability issues. Anyone have any suggestions? Thanks
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I had the same issue with my 2000 4runner 2.7. I couldn't figure it out for the life of me. New modulator, new vacuum switch, new egr valve, new temp sensor, cleaned the EGR pipe, but still had the code. Then I found a exhaust leak at the back of the manifold just before the upper exhuast pipe. It was small bit it was enough.
#5
What sovled the P0401 in this instance?
I have the same issue, cleaned out the carbon and replaced a few vacuum lines but still have the fault. On a budget and need to get through state emissions test ASAP
I have the same issue, cleaned out the carbon and replaced a few vacuum lines but still have the fault. On a budget and need to get through state emissions test ASAP
#6
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Too bad the OP never posted his solution. Everyone should, for the benefit of those with the same symptom. I had this issue (P0401), and solved it by removing, cleaning, and re-installing the EGR temp sensor. After the first cleaning, the 0401 came back after 2 months, then I did a more thorough cleaning (scraping the black crude off with a knife). That did the trick. Next time, I'll just replace it.
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Sorry it took so long to post my solution
I replaced the parts I mentioned in the op but they did not fix the problem. After a couple more weeks of problem free driving I opened the hood to have another look around because that light is annoying. That's when I finally spotted a cracked vacuum line. I guess the crack finally got big enough over a 3-4 month period to be seen. It was right on top of the motor staring at me when I opened the hood. It was the shortest vacuum line on the truck, only 2-3 inches long and it bends at almost a 90 degree angle. I ran to the parts store and they cut me a short piece for free. I took it home, got it worked back on the fittings and the light went away. Check your vacuum lines thoroughly.
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