Had a check engine light come on.

took my paperclip jumper and went from the Ten to the Gnd.
At least that's what I was supposed to do.

I did the Gnd at the far passenger side of the block not the one on the
driver side.

As soon as I turned the key, I see a flame in the Diagnostic box.

Turned off the key and made sure the fire was out.

Haven't tried anything yet. It looks like the flame did melt some of the plastic.

Any thoughts on how big a mess I've made?

Thanks.

 

Try to see if car run fine.....

btw the mazda diagnostic box is crap....if car run.....

 

get another one from Fritz

 

I'd be very concerned about starting the car again. You obviously shorted the box somehow and if it actually caught fire you have possibly burned away the plastic dividers between the electrical contacts. I would at least replace the box before trying anything. Another short of the wrong kind and you may fry your ECU.

 

First off, I'm not really sure how its possible to have that happen. GND obviously goes to common chassis ground, while TEN goes to the ECU for the purposes of diagnostics.

It is possible that the ECU could have been damaged in the process, because its had a dead short to ground applied through it, for a long enough period that its heated the paperclip/connector to the point that something's caught fire.

Rather than start and drive the car, if I were you (and I use my car like you, as a daily driver with the stock ECU as well) I would CAREFULLY attempt to run diagnostics again- bridge the proper terminals and see if the LED does light up with the key in the ON position. Have a helper stand by the diagnostics connector and watch for flames when you do this.

If the LED fails to light up on diagnostics when you try this, then your ECU may have been damaged. Starting the car after this point is at your own risk.

Stock ECUs run for about 100 bucks or so on Ebay. You could just replace it or keep a spare handy as I do. Be sure to match the serial number of your current ECU to the one you buy (IE N3A7 18 881 or whatever number on the ECU should match the one you buy)

Let us know how it goes. Also, I made this especially for you:

 

It's most likely that you didn't get the paperclip in the correct holes. If you went from 12v to ground, for example, it's melty time.

Dale

 

I still have the battery unhooked, but here's what it looks like.

 

has anyone replaced the diagnostic box? Never had it off, is it a big deal to do?

Thanks

 

Does it matter? Yours is fried so it should be replaced regardless of how much of a pain it is or isn't.

 

It's fairly simple. Just depin the box and take note of the placement of the pins. The hardest part will be finding someone willing to cut the connector off the front ring harness. Hopefully none of your wires burnt up.

 

I know this can sound stupid......

But...if yoo don't want to try starting up the car....then try to see if ECU and other stuff work....

Probably your car can run fine without the diagnostic box.....in this case just remove the plastic...and keep the cables separated...and you can at least drive your car when searching for a new diagnostic box....

If ECU and other stuff is OK

 

Found one with Fritz (as usual).

I will check things out tomorrow, hopefully nothing was hurt below the top plastic.

Thanks

 

Looking at the burn pattern (and my 94 shop manual), it looks like you missed the TEN terminal. In the first (clear) picture, and looking at the pins to the left of the valley between the two banks of connectors, it looks like you had one end of the clip in the top left terminal (B+). It should have been the one right below it. Looks like you used the GND terminal next to the just above the IG- terminal in the right bank of connectors.

 

I know you already got one from Fritz, but Mazda used that same box on most of their '90s cars. Mine was busted when I got the car, I got one out of the junkyard and pulled the pins out of the bad one and inserted them into the new one. It took some care, but didn't take super long.

I think you're fine to hook the battery back up. The jumper wire is what shorted it out, and as it is now it's all open circuit, nothing to short.

Dale

 

Thanks.
Just put the battery back.
Car started fine with no CEL or buzzers, so maybe I dodged a bullet.

 

Nice^^

And that damn diagnostic box is really useless ^^