Use and Interrogation of the Diagnostic Connector
 

Does anyone know where I can find a guide ONLINE for this.

supposodly it:

This manual explains the functions and uses of that mysterious black box located near the air filter-the diagnostic connector. The procedures apply equally to most models of Mazda MX5, Miata, and Eunos Roadster 1989>1998. The purpose of this manual is to enable the home mechanic or independent garage to access the self diagnostic facilities of the MX5 which are normally only available to Mazda dealers through the use of their factory provided service tools. Includes a free DIY led probe to get you started!

cheers

miata.net garage

do you have alink as a shop in the uk is charging ££££ for a guide and a wire with an LED oon it.

cheers

anyone.?????

I really think my rich running is down to the thermosensor at the back of the engine under the coilpack....:confused:

go get a led from whatever electronic parts store you guys have over there, then look at the guide in the m.net garage.

sorry but is that what i am supposed to be looking for:

http://www.obdii.com/codes.html

cus that to me is just some random figures.

it does not tell me the procedure.:confused: :confused:

no tabs that isnt for your car mate. Ill have a look for the Mk1 codes.


here you go.

http://autorepair.about.com/library/...l-dtcs-25a.htm

nice one. your a star.

what do I do with the 12v Led now??:confused:

thanks.

Now where does the 12v led come into it?

don't need it for us spec cars.

you'll need a 470-600 ohm resistor to make the led work properly w/o burning it out...

Except that shows a code for an EGR which a 1992 does not have. I'd use the m.net chart instead.

FWIW, I removed the diagnostic connector from my '91. You would not believe how much wire is used for that thing (probably not an issue for most of you but I bet it was over 100 feet!).

Here is a pic I found of the AFM wiring (gives you an idea of what is on the diagnostic connector:

http://ww2.lightweightmiata.com:8080...e/rewire11.JPG

thanks guys!

:vash: :vash: UPDATE:

Finally did this today and it threw code: 17.

I am getting Just over 250km from a tank of petrol on mostly stop/start journeys.

O2 Sensor!!!:vash: :vash:

This is my second 4-wire bosch sensor this year.

I believe the problem lies somewhere else now why it keeps killing the o2 sensor..!!

Any ideas what could be causing the problem?


Water thermosensor?

bad wiring?

Injectors leaking?

Fuel filter clogged?
The use of the Vortech FPR with Emaanage and 1.8 injectors surely cant be causing an excessively rich mixture can it?

The car is also missing...but there is another thread on this!!:confused:

Any helpful replies are welcome

From what I am told, overly rich conditions will kill an O2 sensor. However, just because you throw an O2 code that doesn't mean the sensor is dead. I regularly get a check engine light on my wife's "very rich for a few more days" Miata. As soon as I let off the gas the light goes away and I don't believe the sensor is actually dead.

You can throw an o2 code if the sensor is good if the car constantly runs rich. The ecu is looking for rich/lean/rich/lean, if it stays rich (due to a problem with a different sensor) for a set time, it will also throw an o2 code.

my suspicians point to a bad water thermosensor at back of engibe under coil pack.


Or a sticking AIR FLOW METER.

Both are directly involved wit air/fuel.

Gonna order new thermosensor and get hold of a second hand AFM once Xmas is over nd will report back.

Is your bumper black? Are you plugs white?

plugs are coked in carbon

tail pipes are black

Go to the auto parts store and buy an under hood (or hand held) fuel pressure gauge and check your pressure. I believe your super rich condition could also be leading to a "missing" symptom.

Update:

so I took it to a 'mazda' garage.

he believes the missing is due to a faulty coil pack and the rich conditions are due to a faulty AFM.

i have never changed these since owning the car.

I have sourced a good second AFM and coil pack.

I have also got myself a new water thermosensor, new PCV valve and plugs.

will fit these and report back.

I burned a 1/4 tank in less than 10 miles once when my AFM died...but thats when it actually freaked out, I'm surprised it actually ran lol

just fitted the afm.

O2 sensor has died unfortunately. I can tell as it is no longer oscilating on my a/f guage. I ordered another 4 wire today.

Had a short drive and it may be too earley to say......but the car is allot more responsive, does not bog down and feels faster.

Will monitor over a week and report back.

Tomoz the water thermosensor will be replaced and so will the coil pack.

Fingers crossed.:cool:

if you've added the 4-wire O2 sensor, do you have it wired so the heating element will turn off after it warms up? if you have it wired to a constant 12+v source, it could be killing it prematurily.

I opened mine up to tighten the spring. A few weeks later my wife and mother in law took my car on a trip and broke down 2 hours from home. The spring had broken. I drove up there to get them and drive the car back (women are so damn stupid) and it used an entire tank of gas in about 100 miles.

The 4 wire o2 sensor has been wired as per the instructions on hakuna miata:

http://www.miata.net/hakuna/0004/aindex.htm

Also I changed the water thermosensor, coilpack and pcv valve yeasterday.

Did not notice anything apart from the fact its not hesitating now.

When i get the 4 wire sensor I will fit and monitor for a few weeks.

I am hoping my over rich condition will be cured now!::crx:

How did you wire yours to turn off? Looking for some ideas...

FWIW, I have never heard of killing your O2 sensor faster this way. I have my doubts that it works like that (12V heat kills it but 1500 degree exhaust does not) but I am open minded. What do you know about this?

I talked to someone about this today. Their comment to me is that the factory units (on 4-wired cars) are on all the time. So, no, I don't think there is a problem running it all the time. That is, IMHO, not what will kill an O2 sensor.

i have changed the 4 wire o2 sensor.

before it was throwing code 17 - Oxygen sensor (output not changing)

but it is still hesitating and the MPG does not seem to have improved although my AF guage is now oscilating a gain.

could I hae wirw the heater wires incorrectly?

I have not checked for codes since the install tho.