I know this question has been asked a lot but the files for the 90 ecu schematic have been lost. Anyone have a ecu schematic for the 1.6's? I've looked online and nothing i've seen has been consistent. One of them is telling me the power is this rinky dinky lil blue wire, but i have a hard time believing that

 

i used the one marked as voltage back up for my EMB power source because it was a more realistic gauge of wire

http://www.plxdevices.com/ECUDatabas..._MIA_90_95.pdf

 

Boy, that's not even close to resembling the ECU of a '90-'95 Miata. I don't know who PLX is, but they fail.

You can get some dumbed-down schematics here: http://www.madracki.com/miata/wiring.html

And here are the genuine article for the '90-'93, freshly scanned from my FSM:




White/red at 1B is the main switched feed. You do NOT want the "back up" blue/red wire at 1A, or else your EMB will always be on.

 

i don't have my power run to the blue/red wire at 1b, i have it run to the thicker white/red wire at 1a. Also i know not to connect my TPS wires to the EMB, but i don't seen in the manual where it says TO connect them, all i have connected to the main harness is power, ground, rpm, wiring for flap type sensor, and the ignition harness

 

I've never done an EMB, so someone else is going to have to chime in here. Your list looks pretty complete aside from the injector wires- I believe that you need to split each factory wire out onto a pair of EMB wires- page 23 in the manual.

 

Is the thicker white/red or the thinner blue/red wire the one i need to use for power?

 

You want to take power from the white/red wire, not the blue/red wire. The reason for this is simply that the white/red one is switched by the main relay, whereas the blue/red wire is always on (even when the key is off). If you were to hook up to that wire, the EMB would be on all the time.

It takes a surprisingly small amount of power to run an ECU. They sink a lot of current to ground (through the injector channels and various other solenoid drivers) but they don't actually consume much power themselves.

 

thx ! i already have it spliced into the white/red, i thought the red/blue looked kind of small to be the main power line (even though the greddy schematics were showing me to splice into it)

 

BTW, you see that note I scribbled on the first page (near the ignition coil) describing the 1/4 and 2/3 designations? Ignore that- it's backwards. I have no idea how I screwed that up, but I did.

 

ok i've checked and the O2 sensor position on the harness is 2N. I've already got my EMB wired in and am currently wiring in the O2 clamp. It says to cut the O2 wire feeding to the ecu, while there is one wire leading into 2N, it travels into some tape with another wire and 3 wires come out the other end (different colored/gauge wires too!). The wire feeding the O2 gauge under the hood is black, none of the 3 wires coming out of the mysterious tape are black. So do i need to cut the wire feeding directly into 2N, one of the 3 wires that goes into the tape that 2N runs into, or back track the black wire from the O2 sensor and see which color of the 3 wires it is?

 

You want the Red/Blue wire at 2N. The black plastic business is Mazda's interpretation of a shield.

The wire to the sensor is only black at the sensor itself. At the point where it connects into the front harness at interconnect B1-19 (under the hood, behind the head) it's Red/Blue.

 

aight i got that wire cut and wired appropriately. What is up with the wire without insulation running inside the tape near the other two? Thx again for the help Joe!