NB8B Diagnostic connector.

slyfox2151 · Postby **slyfox2151** » Thu Oct 02, 2014 3:21 pm

Hello, So i was checking fault codes yesterday on my 2002 thats not OBD2 compliant, and i managed to short the wires from the B+ / fen to the ten / ground. This promptly blew the engine fuse in the cabin.
I have replaced that fuse and the car starts and runs again, But I'm no longer getting any codes (pulses) from the LED.

When I first turn the key on the LED glows for about half a second and then turns off, that's all that happens, No repeats or anything. Is there another fuse or common fault that I might have caused an issue with?

EDIT: I bought a new resistor and LED to make sure thats not the problem.

Caffeine · Postby **Caffeine** » Thu Oct 02, 2014 5:27 pm

The LED will turn on briefly when you turn the key, and after that it should blink any error codes.

Sounds like you don't have any errors

slyfox2151 · Postby **slyfox2151** » Thu Oct 02, 2014 5:53 pm

I hope that is the case... Will wait a few days and check again for a code, maybe ill try forcing a code to double check its still working.

The guides for checking the codes say it should light up for 3 seconds when you turn the key, but its lucky to be lit for ½ of a second.

Caffeine · Postby **Caffeine** » Thu Oct 02, 2014 5:55 pm

slyfox2151 wrote:I hope that is the case... Will wait a few days and check again for a code, maybe ill try forcing a code to double check its still working.

The guides for checking the codes say it should light up for 3 seconds when you turn the key, but its lucky to be lit for ½ of a second.

Is it when you start the car? There's a very brief LED flash to indicate the ignition pulse.

slyfox2151 · Postby **slyfox2151** » Fri Oct 03, 2014 1:08 am

Caffeine wrote:Is it when you start the car? There's a very brief LED flash to indicate the ignition pulse.

No, its as soon as I turn the key to "ON" or Run, not start. Can hear a relay trigger and the light goes out with it.

I will go for a long drive tomorrow and then check for any codes. Will report back.

slyfox2151 · Postby **slyfox2151** » Sun Oct 05, 2014 1:38 pm

UPDATE:

So I have dríven a good 600 ks and have just checked for codes again.

The codes I am getting are,
11 Null
13 Null
14 Atmospheric pressure sensor
15 Oxygen sensor (output too low)

Is it likely that I need to replace the atmo and oxygen sensors or what should I do from here? Fuel consumption is still good, 7.8L/100km

Video of codes.
https://www.youtube.com/watch?v=1VGbos9 ... e=youtu.be

93_Clubman · Postby **93_Clubman** » Mon Oct 06, 2014 11:50 am

slyfox2151 wrote:Is it likely that I need to replace the atmo and oxygen sensors or what should I do from here?

If you haven't already, then it would be best to reset the ECU to ensure these error codes are current, as the ECU stores a certain amount of error codes unless cleared.
Obviously best to avoid the possibility that these are old error codes if the ECU wasn't reset after possible past issues so that you know you're dealing with current error codes. Reset the ECU by disconnecting the battery & pumping the brake pedal half a dozen times.

slyfox2151 · Postby **slyfox2151** » Mon Oct 06, 2014 12:22 pm

ECU was already reset.

Before the reset I was also getting error code 10.

93_Clubman · Postby **93_Clubman** » Mon Oct 06, 2014 2:15 pm

Given the info about shorting wires in your post above, if you haven't reset the ECU to clear the codes since shorting the wires, then it would be worth doing again.

If you have reset the ECU since shorting the wires, then code 15 sounds like you need to replace the O2 sensor. Could also be worth giving the Mass Air Flow sensor a very careful clean with MAF spray cleaner & cleaning up both sides of the MAF connector as that could also help with the previous code 10. Ref code 14, response is not so clear, but keep in mind replacing the ECU in an NB8B also requires matching (to the replacement ECU) immobiliser & keys (& locks): http://forum.miata.net/vb/showthread.php?t=316126

slyfox2151 · Postby **slyfox2151** » Mon Oct 06, 2014 3:20 pm

Well, Lets hope we don't need to replace the ECU then

, If I manage to fix the other codes but still get 14 I might try some compressed air on the atmo sensor.

Ecu was reset after shorting, which is why I was only getting a single flash... Is there a guide on replacing the NB8B o2 sensor? I have tried searching but come up with nothing. I found this sensor http://www.mx5parts.co.uk/oxygen-sensor ... -3412.html seems to be the correct one but I'm not sure if there are cheaper options.
Preferably located in brisbane.

I assume the sensor is up near the exhaust extractors?

( My last car was a diesel with a lot less electronics

)

93_Clubman · Postby **93_Clubman** » Tue Oct 07, 2014 10:39 am

slyfox2151 wrote:Is there a guide on replacing the NB8B o2 sensor?
Guides tend to be found on the US forums like Miata.net, so try Googling: miata replace oxygen sensor

I found this sensor http://www.mx5parts.co.uk/oxygen-sensor ... -3412.html seems to be the correct one but I'm not sure if there are cheaper options.
There could be cheaper, but that PnP one is well priced.

I assume the sensor is up near the exhaust extractors?
Yes