OBD Code P0404
08-06-2018, 05:42 PM
#41
Keep Right Except to Pass
Thanks for this thread. My '04 TL was in two weeks ago for an engine misfire (flashing CEL—had the car towed). I didn't get to drive it again until yesterday, at which time the CEL came back on and threw a P0401. Post #13 was essential: The grey wiring harness seen there was unplugged. Reconnected it and the problem is solved. Didn't even have to open up the assembly.
04-05-2021, 07:15 PM
#42
Advanced
Good evening.
I'm reviving this old post in hopes that someone else has had the same problem that are seeking solutions.( 07 TL Type-S.) I recently received a P0404 DTC during a long road trip, along with some very rough idling and almost "misfire-like" symptoms while idling or accelerating. At first I thought my transmission was the issue, but observing the fluid and temperature, it was out of the question. The DTC did not trigger right away, however when it did, I knew immediately that this was a generic EGR DTC. Upon inspection, the EGR valve itself had a piece of carbon stuck to the valve, not allowing it to close properly. The following day, I went ahead bought a new EGR gasket and a large can of carb cleaner. To further prevent this from happening again the future, I went a few steps further and removed the upper plenum, along with the butterfly valve. During that removal process, I used the carb cleaner to clean the EGR passages, along with the upper plenum EGR passages. It took a good three hours since I wanted to be diligent. After reverse-installing everything, the car started right up without a hitch, and the idling has gone back to normal. Acceleration and drive comfort has also improved. I would say if you're having a similar issue with the EGR/rough idling, go the step further to clean those passages out. It helps out tremendously. It may also improve with fuel mileage.
I'm reviving this old post in hopes that someone else has had the same problem that are seeking solutions.( 07 TL Type-S.) I recently received a P0404 DTC during a long road trip, along with some very rough idling and almost "misfire-like" symptoms while idling or accelerating. At first I thought my transmission was the issue, but observing the fluid and temperature, it was out of the question. The DTC did not trigger right away, however when it did, I knew immediately that this was a generic EGR DTC. Upon inspection, the EGR valve itself had a piece of carbon stuck to the valve, not allowing it to close properly. The following day, I went ahead bought a new EGR gasket and a large can of carb cleaner. To further prevent this from happening again the future, I went a few steps further and removed the upper plenum, along with the butterfly valve. During that removal process, I used the carb cleaner to clean the EGR passages, along with the upper plenum EGR passages. It took a good three hours since I wanted to be diligent. After reverse-installing everything, the car started right up without a hitch, and the idling has gone back to normal. Acceleration and drive comfort has also improved. I would say if you're having a similar issue with the EGR/rough idling, go the step further to clean those passages out. It helps out tremendously. It may also improve with fuel mileage.
04-13-2022, 12:46 AM
#43
Not to resurrect old threads, but this solution helped me fix my 2005 TL (121k miles). There were no less than 3 carbon chunks holding the valve open. Cleaned them out good and it started up right away. Thanks for the help!
My CEL originally started off when going to work, and it felt like an occasional misfire. I thought it might be a coil, but this proved to be a much cheaper solution.
My CEL originally started off when going to work, and it felt like an occasional misfire. I thought it might be a coil, but this proved to be a much cheaper solution.
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