Help with replacing CPU
 

Okay I personally am not doing it but I was wondering how difficult it is and how long would it take the average person who knows Mazdas to do. Also are they preprogrammed or does one have to program them themself

CPU = body computer (controls Horn, warning beeper, turn signals, Hazard lights, etc)

ECU = engine (or emissions) computer.

The CPU is in the drivers kick panel and just requires pulling the kick panel cover off and one 10mm nut, while the ECU is found under the passengers floor board at the firewall, and has 8 screws and nuts to undo.

They both will have at least 3 plugs on them.

either one should take about 5 minutes to remove. the stock equipment does not need reprogrammed.

Ok well meant the ecu....sry dont know much about electrical..but I have no pulse in my injectors and before I had no spark...but my main relay was blown so I got the no spark problem fixed but dont have any pulse to my injectors. So Im thinking I need to replace the ECU.

What year, and is it turbo?

1991 Na

Did you really mean your MAIN FUSE was blown in the fuse box in the engine bay?????

Check and make sure the ENGINE fuse in the interior fuse box is good. But if you jumper the yellow, two socket fuel pump check connector near the boost sensor on the right front strut tower, and put the key to ON, and now you hear the fuel pump running, then the ENGINE fuse has to be good and no since looking at it.

The ENGINE fuse is used to pull in the MAIN RELAY and Circuit Opening Relay. Main relay supplys power to the ECU and the Circuit Opening Relay supplys power to the fuel pump. So, you see, if the ENGINE fuse is kaput, the engine isn't going to work. IT's rare the ECU is bad if it's been working recently.

If you were a touch electrical, I'd suggest pulling the plug off the ECU and checking the four fuel injector wires there for batt voltage with the key ON. That'd prove the Main Relay is supplying power to the fuel injectors.

Did your battery get put in backwards recently??? for a moment?

Okay no wasnt fuse my main relay was shot replaced it and now have spark. Also I found a bit of water on the connectors for my ecu..so um thinking I got some water in and fixing that. But as of now no pulse to injectors.

Note: This is what happened if it gives any indication Driving one day and dropped someone off...went to start my car nothing...waited for awhile and it stared for some reason anways on the way home died. Did this twice and now wont start at all but will crank over. I have checked all the obvious stuff and no this is not fuel related...pressure, pump, ect. it all works. However thanks for comments so far...appreciate it.