Several warning lights on

What is your question?

2005 Mazda 6-Runs fine. Warning lights all came on at the same time. Engine, brakes, ABS, traction control, AT, TCS off, speedometer not working. At random times, all lights go off except Engine, brakes and AT, then speedometer starts working. Replaced ABS speed sensor, still not working, OBD Code U0121, dealership could not accurately pinpot the issue, recommended replacing the instrument cluster at a substantial cost with no guarantee that will fix the issue. If we put a used cluster in it ourselves, does it have to be programmed by the dealership or can we install it and the car will still run with no programming necessary? And do you have any other recommendations as to what the issue may be?

What makes this problem better or worse?

n/a

How long has your 2005 Mazda 6 had this problem?

1 month