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Discussion Starter · #1 · (Edited)
Condensed story; 06s approaching 90,000 miles. 2013-09-23 morning commute had the car idling for 1.5 hours. It was fine when I parked it. I had no observations.

Drive home 9hrs later. I notice its being kinda grab @ss with the throttle and the idle is down about 100 RPMs but not missing. Just low, thus making the "take off" feel kinda strange. So i plug in the OBDII blue tooth reader and get the Android Torque app spun up. No codes, no DTC's, so I start watching the O2 sensors on bank 1 & 2. Kinda ratty at times but NBD.

I make 3 diferent stops just walking away from the car after shutting it off but leaving the app running. On the last round I'm just about home and wanted to read the values from the PIDs. The APP reports lost communication with the ECU and BAAAAAAAAM the rear brakes are applied almost skidding on the wet road. MIL for CEL and ATX come on and I feel the anti-lock pulsing the pedal. I turned the car off and the brakes let off. Turn key on and ATX mil is lit, car is in 3rd gear CEL is on but not flashing ATX MIL is on. I pull over and get off the main road turn the car off. I pulled the OBD dongle and started it. CEL is on, ATX MIL is off. OK - I plug in dongle and get a read - U0100 network, U1900 Network/ABS.
Figuring my probing caused this I disconnected and drove for 5 miles. Alls is well. Connect and scan one more time. Only the U0100 code remains. So I cleared it. Car drove fine today.

I found this on several different sites. Take away - That could have ended badly, use caution when pulling the ECU/ECM for codes. I did it while driving and created some one off anomaly triggering the ABS unit! BE CAREFUL!!!

Service bulletin:
Originally Posted by Mazda USA, CA
Bulletin No: 01-002/05 Last Issued: 01/13/2005

All 2003 - 2004 Mazda 6
2005 Mazda 6 2.3L only


Some customer vehicles may have a false MIL illumination with multiple U-code DTCs. This condition may be caused if the WDS DLC cable is connected or disconnected while the ignition switch is in the ON position, or when the engine is idling. IMPORTANT: When connecting or disconnecting the WDS DLC cable (or any scan tool equipment) to the DLC-2 connector (under dash), the ignition switch must be in the OFF position, otherwise, the MIL light may come ON and false CAN communication DTC codes may be set in the different CAN bus modules. The following DTCs may be stored if this condition occurs:

NOTE:It has been reported that some customer vehicles have failed the state emission OBD II test. This may be caused by the inspection station connecting or disconnecting the DLC cable when the ignition switch in the ON position, or when the engine is idling. Customers having this concern should have their vehicle repaired using the following repair procedure.

1.Verify customer concern.
2.Erase all DTCs.
3.Turn OFF MIL.
4.Turn ignition switch to OFF position.
5.Disconnect WDS DLC or scan tool cable.
6.Verify repair.
NOTE: do not return vehicle to customer with MIL illuminated.

There is a PDF of this!!

(( Granted, it says it was fixed but clearly its not 100% (read the forums), plenty of other cars have had this issue Ford and Mazda from 2003 to 2007 ))


3,608 Posts
I had this (edit: for clarification, I mean the random U codes) happen after an inspection a few years. I just figured the shop fucked up the scan, but didn't care because I passed. :)
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