Jaycar DFA, and 02 Sensor wiring issues *Sigh*

RG.net · Postby **RG.net** » Wed Mar 10, 2010 10:44 am

Anybody have any ideas? (fatty?)

Fatty · Postby **Fatty** » Wed Mar 10, 2010 11:00 am

remove the wire from the dfa and crimp or twist it together but leave it exposed so you can probe the wire with you multimeter. while the car is running (multimetre set to read voltage), if you have the correct wire you should see the voltage rise and fall , and it should also oscillate rapidly when the car is warmed up and idling in closed loop.

if the voltage remains a constant 5v (which incidentally corresponds to load point 128) then i suspect you have tapped the power feed wire to the airflow metre, instead of the output of the meter.

RG.net · Postby **RG.net** » Wed Mar 10, 2010 12:40 pm

That makes sense, I'll give it a shot when I get home. in the mean time, Does anyone happen to know what the AFM signal wire colour is for an NB8A? Or have the wiring diagram for the RHD models would be great, all I can find is the American diagrams, and they are pretty much useless.

RG.net · Postby **RG.net** » Wed Mar 10, 2010 4:04 pm

Ok, so i've just done a quick test with the multimeter.

The wire i have tapped sits on roughly 2.5 volts when on idle, once i touch the throttle, it will increase to no more then 3.5 volts. It doesn't go lower then 2.5 volts by the looks of things. Its a very slow reading for it to be the right wire i'd assume.

So, i have three wires to my AFM, green with black, black with blue, and white with red. The Green/Black is the one i have tapped. i guess i'll need to splice the wires near the AFM plug, put the multimeter on it and see which one decides to oscillate.

Fatty · Postby **Fatty** » Wed Mar 10, 2010 5:22 pm

just stick a pin into the wire and then put the aligator clip from your multimetre onto that. much easier than splicing the wire.

once you've found your wire at the air flow metre, use some educated guessing at the wiring harness near the ecu, and stick a pin in whichever wire seems to be your best guess. set the multimetre to read resistance, and read the values between the 2 pins, and if you've got it right you should find that there is very low (equal or close to zero) resistance between the 2 pins (you may need to use some extra wire to "extend" your multimetre wires). if the resistance is very high, you've got the wrong wire. take another guess, insert pin in wire and test. keep repeating until you find the correct wire.

Fatty · Postby **Fatty** » Wed Mar 10, 2010 5:25 pm

ah sh*t hang on, forget the oscillating thing. i just realised i was getting confused with the o2 sensor :oops:

but yeah, it should rise and fall pretty rapidly, not slowly. but apart from that, from what you're describing it sorta sounds like you may have the right wire

Fatty · Postby **Fatty** » Wed Mar 10, 2010 5:49 pm

and just one more thing that pops into my head as a possible problem. the dfa can be configured to work over a 0-5v, 0-12v, or 0-1v range. most airflow metres are 0-5v but maybe the micra is an oddball and is 0-12v ? therefore the dfa needs to be reconfigured. it's a longshot and can be easilly dismissed once you know for sure how the dfa has been set up (or just confirm how the micra afm works)

i don't have my instructions handy but there is a test procedure that explains how to check and calibrate everything. it may be worth running thru that.

RG.net · Postby **RG.net** » Wed Mar 10, 2010 6:13 pm

Fatty wrote:ah sh*t hang on, forget the oscillating thing. i just realised i was getting confused with the o2 sensor

but yeah, it should rise and fall pretty rapidly, not slowly. but apart from that, from what you're describing it sorta sounds like you may have the right wire

I just realised i had the multimeter set on a high level, making the voltage changes appear slow :lol:

That has to be the wire, the red/white just shoots to the end of the scale, the black one does nothing at all.

RG.net · Postby **RG.net** » Wed Mar 10, 2010 6:16 pm

Fatty wrote:and just one more thing that pops into my head as a possible problem. the dfa can be configured to work over a 0-5v, 0-12v, or 0-1v range. most airflow metres are 0-5v but maybe the micra is an oddball and is 0-12v ? therefore the dfa needs to be reconfigured. it's a longshot and can be easilly dismissed once you know for sure how the dfa has been set up (or just confirm how the micra afm works)

i don't have my instructions handy but there is a test procedure that explains how to check and calibrate everything. it may be worth running thru that.

MMM, this could be the only possible thing that is left.

The micra has a MAP sensor believe it or not! the DFA originally came off a R31 skyline though. That could explain why it doesn't respond when the car is on i guess. i'll give the booket a read tonight and see what i can come up with.

Thanks for the help so far Fatty

Fatty · Postby **Fatty** » Wed Mar 10, 2010 6:31 pm

aaaaaah, ok most map sensors, as far as i know, operate on a 0-12v range! i think that may be the issue! it should be pretty easy to re-wire it for 0-5v, which will then make it compatible . i hope :lol:

RG.net · Postby **RG.net** » Wed Mar 10, 2010 7:20 pm

Fatty wrote:aaaaaah, ok most map sensors, as far as i know, operate on a 0-12v range! i think that may be the issue! it should be pretty easy to re-wire it for 0-5v, which will then make it compatible . i hope

Ah well there you go!

Now i've been looking through the booklet about recalibrating it, but it's kinda confusing me

i remember seeing how you had it set up on the bench and all that jazz. Its not exactly telling me what to do to calibrate to a certain voltage ... unless i am missing a few pages :roll:

Edit: found this just recently

will give it a read tonight. http://www.autospeed.com/cms/article.html?&A=2420

edit, looks like I need to jaycar and buy myself a pot so I can set it up properly.

Edit, can't find much about actually configuring the damn DFA.