99 miata shut off doing 65mph and wont start
 

Hey guys going to need some ideas.. Car died doing 65 mph today and wont restart. Brought it to a friends shop and obd2 wont link up.. there is power going to obd2 because scanner is lighting up immediately after being plugged in. I did have a recent CEL after moving my o2 sensors around in order to put my wideband in the pre cat o2 bung in header. I moved #1 o2 into the #2 spot, and #2 o2 into a wideband bung slightly downstream.. could this be the underlying issue? has to be related.. anyway car is a 99 with stock ecu. also don't hear the fuel pump priming when I turn on key.. I have a feeling ecu is some how fried but I heard it was pretty unlikely.. sorry for the jumble of words but any help would be much appreciated.. thanks

I think you can still jump an NB's fuel pump with the diagnostic box. FP and GND with a piece of wire.

Check your main relay too.

I had the same problem in my 99 running on the stock ecu. Turned out to be a bad o2 sensor and or harness. The rear o2 sensor wiring had worn through the insulation by making contact with the rear cat converter heat shield. That shorted it out and it kept blowing fuses. There was one fuse in particular that it kept blowing that lead to the same situation you have going on now. Can't remember which one it was, possibly room?

Either way I just said ef it and got rid of the o2 sensor and replaced the fuse and haven't had a problem since. If i remember correctly on the 99 the fuel pump is grouped with some other stupid fuse in the fuse box.

Start there.

main relay is fine but in think erock might be right on the o2 wiring I did extend them.. thanks guys I will let you know what goes on

so I found that the second o2 wire had in fact worn thru and shorted.. Main relay looks fine, although I didn't test it but I ordered a new one for 18$.. I checked most fuses but I don't think the load made it to there.. All main fuses are fine..if it isn't the main relay, what else could it be? either way I will update tomorrow am.. thanks again guys

You should be able to un-plug the second o2 and the car will start up provided all the fuses and relay's are g2g. This particular issue happened to me several times as I replaced the blown fuse and went about my business not knowing what caused it... only to be stranded on the fwy 15 minutes later with a fuse box full of garbage.

From my experience with this issue, I would check every single fuse in the interior fuse box. It seems like mazda didn't put enough circuits in these cars and started just tagging shit on for no good reason.

FWIW even though i had the short/shutdown issue several times my relays never had issues... still running on the same ones.

Erock you were right, was a 15 amp fuse labeled ''engine''... man do I feel dumb.. appreciate all the input guys.. main relay was fine didn't need to replace but now I have an extra..

I had same issue just recently when a metal wrench in the trunk was shorting out the battery while driving....no signs of something wrong until the car died on the side of the road with dead battery and wouldn't start.

Awesome man. Glad I could finally give something back to some one on this forum. God knows I do enough leaching around here to require about 1000 posts of useful information to make up for it.

much appreciated erock