2008 Mazda 6; I4; 2.3; 5 spd OD
Randomly, while driving the vehicle, all of the dash indicators will turn on (traction control, check engine, e-brake, etc). The car continues to drive normally and the only way to "reset" all of that is to turn the car off and back on again.

Is that a sign of a failing ECM?

--Brian

 

YES one sign, but you are not really giving enough information to conclude a failing ECU.

You need to check the OBDII for DTC stored. Most likely in the monitors so see if they are all READY.
It would also be good if you are automatic to check the TCM codes as well.

While you are there or getting ready to say I dont know how or don't have a good quality Scan tool...
have your battery health checked.
Look carefully and perhaps service all the battery cables at all their points of contact.

 

So...first off...THANK YOU for pointing me to the other things to check. I had no idea what else to check. Ok...so...here is what I found using the OBDII scanner and the FORScan software (just so you know what I'm using to get the codes):
TCM code - P0841-FF
PCM code - P0126-FF
OBDII code - P0126C

I looked up each code...The P0126 might explain another random problem that has happened once or twice...the transmission indicator lights on the dash will go out and the transmission will either not shift up, or it will shift down by itself, like I put the shifter into a lower gear while driving.

So...I might have been chasing the wrong thing here thinking the ECU is faulty...it seems I've got a few issues to clear up related to the transmission.

 

Good work.. Take care of diagnosing each DTC and I think you will likely resolve your problem. You might also clear all DTC and re-set the monitors and do a couple of complete drive cycles to see what DTC appears to return?

 

One of the codes led me to drain the transmission pan and changing the filter, which turned off the check engine light; Still have the "all dash indicators come on" issue, but one thing at a time. next up a battery check,

Again..thanks for giving me some ideas about what to check.

 

interesting TCMs are different from the ECU, DTC's. It is sounding more like a continuity concern? (guess)

 

P0126 is often caused by a failed or failing thermostat.