Discuss the matter with an Authorized Mazda Dealer. This is the quickest and best way to address the issue.
Mazda 6 Owners Manual: Front combination light removal/installation
Caution
Incorrect servicing of the discharge headlights could result in
electrical shock. Before servicing the discharge headlights, always refer to
the Discharge headlight service warnings. (See DISCHARGE HEADLIGHT
SERVICE WARNINGS)
Note
When the ignition switch is turned to ON, ...
Mazda 6 Owners Manual: Procedures for determining the location of a malfunction
System Wiring Diadram
PCM
1. Check the display of DTC U0121 and/or U0155, using the SST (WDS or
equivalent). (See DTC TABLE.)
2. Referring to the following table, determine the malfunctioning part of the
CAN system.
ABS/TCS HU/CM or DSC HU/CM
1. Accec and monitor the PCM MSG and IC MSGo ...