ok the brown/white wire at the pressure sensor measures a measly .23 volts... that was when it was laying on top of the carpet.. i got to thinking maybe its grounded when you bolt it down so i did that and it then measured .04 volts?!?!?! so something is wrong with my ecu obviously cause its not getting the 4.5 or 5 volts with the ignition turned to ON. i have ordered a new ecu but can anything else be the problem... the plugs were ungodly corroded, the last wire of the last harness (not the long harness) was a blue/white wire and it was completly out of the harness. i cannot seem to understand its function in the wiring schematics. anyhow i just want some info on this and what you would do or what i should do, an ecu is on the way supposedly. thanks in advance

 

Have you checked the other 5V sensors? The TPS, variable resistor, coolant thermosensor, intake air thermosensor and AFM all have a 5V supply from the ECU (brown/white wire).

Does the engine run? If the 5V supply was dead, I doubt the engine would be able to.

 

no i havent been able to get spark is the problem..... ill check those if i can find them, i didnt know you should check all of those.. the car hasnt had spark the whole time, CAS, Coils, ignitors all check out fine with the multimeter

coils = 11.59 volts
cas resistance on both sets of wires = 159 ohms
ecu wires to cas = same 159 ohms
coil resistance = .04 ohms and .03 ohms

the pressure sensor wire was the only one that didnt come out right so based on searching that means the ecu is bad, ill check those other things you mentioned and post them up for you... thanks nzconv

 

oh... and every engine bay fuse tested fine as well

 

I don't know if we've got the same wiring harness or not, but you should be reading 12v at the black/white stripe wire,5v (or so) at the other black wire, and the output voltage (around 3.5 w/ vacuum, 1.5 at idle) is on the brown/ red stripe wire...this is with the pressure sensor in the car, of course...I thought I had a bad one,too, 'cause the output voltage was jumping all over the place when I'd rev it up- evidently it's supposed to do that, 'cause the new one I just put in does the same thing- Shoulda listened to the Mazdatrix guy- he said these things RARELY go bad!

 

If the other sensors I listed are getting 5V okay, then it's not an ECU problem. It's more likely wiring problem.

 

ok i am getting 11.4 volts at the b/w wire on the pressure sensor but nothing on the other two you mentioned wayne.


nzconv... where are the other things you listed and what wire to i test for them as well... also what wire do i test from the ecu that should have 5v? thanks guys

 

i havent tested the other sensors cause i dont know where they are nor was i supposed to check them if i can find them ill post what they are getting voltage wise

 

Do you have the connector ON the boost/pressure sensor while you're checking voltages?

 

just tried that man and no luck its still the crappy .23 volts.. i just measured another brown/white sensor ( i think the temp one) and its also the same .23 volts so its my ecu.... why did this happen? will swapping a new one in fix it? thanks

 

Have you checked the ECU codes? You can't get the car started, right? You sure it's not flooded? Wouldn't be the only rx7 flooded in east Texas this week LOL, I just dealt with that crap...

 

Go to www.iluvmyrx7.com and download the EFI and Wiring Diagrams chapters of the Factory Service Manual. These chapter will show you what and where all those sensors are, and let you trace the suspect circuits and check the ECU.

Having the FSM to refer to when trying to do this kind of troubleshooting makes things much easier.

 

Pin 2A outputs the 4.5/5volt ref voltage. Usually putting a dead short on any of the brown/white wires will kill the usefullness of the ECU for anything but a boat weight. Henrik might know enough about what part could be replaced to fix it.

You NEED to find which of the approx 5 brown/white wires killed the ECU. Which had the dead short. Were you *adjusting* anything prior to the death of the car. Ask yourself that and go to that place of last maintenance to resolve your problem.

 

hailers i see what your saying but the strange thing is the car was flooded before this happened, all i did on the car was the unflood technique... then when that didnt work i investigated and found out i had no spark all of sudden... how do i test to see what wire is causing this because i do not want to plug another ecu in just to blow it thanks guys its a lot of help

 

ok so are there any brown/white wires around the spark plugs/power steering because thats the only thing i messed around with... meaning i was digging into that side of the engine bay so if there is a wire there maybe i bumped it, what is over there with that wire?

 

The things that are using the brown/white are: the afm, boost/pressure sensor, tps, atmospheric pressure sensor and fudge I forgot what else. Its shown in the free 88 fsm that is online. In the Wiring schematics.

Whatever supplies the 4.5/5 volt reference voltage also supplies power to the device that triggers your coil/ignitors.

 

Yeah, like I said...

 

https://www.rx7club.com/forum/attach...&postid=488871 ECUPINSONE
https://www.rx7club.com/forum/attach...&postid=488875 ECUPINSTWO
https://www.rx7club.com/forum/attach...&postid=488879

http://www.iluvmyrx7.com
https://www.rx7club.com/forum/showth...hreadid=163732
http://www.teamfc3s.org

https://www.rx7club.com/forum/attach...&postid=532736


http://www.tequipment.net/FlukeDigital88Multimeter.html

 

wow thanks guys thats a big help, its hard for me to find this stuff in the FSM cause i have it but a lot of it makes no sense to me, im going to try to find them in the engine bay tomm or the next day and test for the short, thanks again guys

 

wow hailers where did you find those pics... i dont see them in any of my manuals but then again i only have had the ones from fc3org.... those pics you posted are huge help to me thanks buddy

 

Yeah. There are only five items coming from 2A in the picture. Unplug all of them and then unplug the middle plug of the ECU and get on pin 2A with your meter set on ohms. One lead to a ground line a ECU mounting stud and the positive on the 2A. It should be an open i.e. not shorted to ground.

One thing to note here: say you had sometime in the recent past, gone to your lead or trail coil and grounded one of the wires that come out of the ECU. That could have whacked the voltage regulator in the ECU that outputs the 5volt ref voltage signal.

I've seen posts on this site where folk have said *I grounded the black bullet ground on the LEAD/TRAIL coil assy and now my car won't start*. Yeah, won't start because he toasted the ECU.

I bought a fried ECU off a fellow who had accidently shorted the brown/white wire on his boost/pressure sensor. I put it in my car and took a look at pin 2A. Back probed it all connected up. It showed a similar figure to what you say, about 2 something volts. No worky like that. But the jacks off the ECU helped make a breakout box for the ECU.

Disclaimer: Your car could be experiencing a different problem altogether that I can't relate to.....so don't sue me if things don't work out.