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Old 05-03-2013, 04:01 PM   #1
Moronix
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Thumbs down OBD2 code "U0401" ?

After installing my Airaid CAI I got this code "U0401" from Hypertec tuner(Not sure the CAI has anything to do with it). I connected my OBD2 reader and it shows a "yellow" light and some flashing indicators..."C, EV, O, CH, E". My OBD2 reader evidently does not show "U" codes but the manual indicates the computer is monitoring these values and hasn't finished yet. So the check engine light is not on. Telling the OBD2 reader to "erase" does nothing since on the next "read" it shows the same indication. Question is will the computer eventually stop monitoring these values and go back to normal or does it really require work?
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Old 05-03-2013, 08:02 PM   #2
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I found this on a google search for that code:

http://ww2.justanswer.com/uploads/sd...ight_is_on.pdf

Not for a Mustang, but that code is for the transmission control module it says.
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Old 05-04-2013, 07:02 AM   #3
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JimC Thanks for the infor but it's for cars with CVT (not Mustang). The code actually indicates something like "invalid data sent to ECM/PCM". I guess something unusual happened and sent the wrong data which caused the computer to start extra monitoring of the oxygen, exhaust gas recirculating system and other stuff. Evidently it's not serious enough to cause the "check engine"lite to come on. I just wonder if it will settle down and go back to normal by itself or do I need to take it to the shop. Since I only have 1300 miles on it, it's in warranty.
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Old 05-04-2013, 11:28 AM   #4
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It might just need a battery disconnect reset and a throttle relearn because of increased airflow.

http://www.allfordmustangs.com/forum...ml#post3483505


Thousands of Airaid CAIs have been installed without issue, so if the issue remains you may have a defective piece of hardware. Good luck.
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Old 05-04-2013, 11:54 AM   #5
157dB
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Old 05-04-2013, 05:30 PM   #6
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Been doing a little reading and it appears my problem may have been created by just disconnecting my battery when installing my CAI. Little more research and a couple more days and I should know for sure.
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Old 05-05-2013, 11:09 AM   #7
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It appears that just clearing a DTC code will "reset" the status of all monitors to a not run "flashing" condition. There are a max of 11 monitors available and all are not used as of yet. A "drive cycle" has to be accomplished or maybe 2 or 3 drive cycles to set all the monitors to a "Done" status (not flashing). Finding the right "Drive cycle" to accomplish is not easy. I found one online and tried it and 2 of my monitors stopped flashing. I did another drive cycle this morning and 1 more monitor stopped flashing. I now have 2 monitors left flashing. They are the "O" and "OH" monitors. I guess tomorrow I will try another "Drive cycle" to see if they clear up.
It also seems that simply disconnecting your battery (per the Airaid CAI instructions) will also reset the monitors. I did both since I disconnected the battery before installing my Airaid CAI. Then when I tried to instll the tuner I got the "U0401" code and tried to reset the code. Don't know what caused the U0401 code and telling the tuner or the OBD2 reader to erase it does not erase it. More later.
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Old 05-23-2013, 07:52 PM   #8
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There is a recall on the 13 Auto V6 When i bought mine it was on the carfax
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