2006 Posted November 13, 2018 Share Posted November 13, 2018 I have a 2018 with about 20000 miles that sets a P0401. I did pinpoint tests W and AZ. When checking flow through the cooler, it passes. Test says the system is working properly. I've probably done at least 100 egr coolers for this code on previous years and the pinpoint test always worked in identifying a restricted egr cooler. This is the first 2018 model year truck I am doing with this code. They have a different egr cooler and bypass valve compared to previous years. Without disassembling anything, I can't identify whats causing the problem. Any ideas? Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted November 14, 2018 Share Posted November 14, 2018 Personally, I find most air management pinpoint tests time consuming and frequently inconclusive. EGR coolers especially AND only twice have I gotten the appropriate code when running the KOER self test. I have gotten into the habit of performing the visual inspections of the intake and exhaust systems which includes removing the air filter element, looking at the MAF sensor and cleaning it as needed as well as popping off the MAF sensor to be sure it is not plugged then, with a P0401 I remove the small EGR pipe and inspect the EGR cooler core for plugging. It literally takes a minute to remove that pipe. If all looks good then I run the PPT's. Yeah, I see you wrote "Without disassembling anything" but sometimes that is the most direct and effective way. Quote Link to comment Share on other sites More sharing options...
mchan68 Posted November 14, 2018 Share Posted November 14, 2018 What is the hour count of this truck, relative to the miles? Higher hour count trucks tend to be the offenders. Quote Link to comment Share on other sites More sharing options...
Popular Post 2006 Posted November 19, 2018 Author Popular Post Share Posted November 19, 2018 Hour count was high. Problem was in the lower intake manifold, in the mixer, where the hot exhaust and cold air meet. Was plugged, causing the code. The pinpoint test does not address this, said everything is normal. In the older trucks, where you check the flow through the egr cooler and monitor maf while cycling the bypass, the maf would be steady, in the mid 30's. With a plugged cooler, it would read mid 30's and mid 50's depending on the bypass position. I was getting high 50's all the time regardless of bypass position. This tells me there is a exhaust restriction downstream of the cooler and the next logical place is in the mixer. After removing the lower intake and cleaning it, my reading went back to normal and the codes gone. 3 Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted December 29, 2018 Share Posted December 29, 2018 Good find and great explanation! Quote Link to comment Share on other sites More sharing options...
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