How do you hook one up? it has 4 wires I'm guessing the red and black are power and ground, but what about the yellow and purple?

 

dDub told me this last night:
On the gauge run the power wire for the light and the power wire for the gauge into 1 single wire.
Run the ground wire from the light and the ground wire for the gauge itself into 1 wire as well.
Tap the single power wire you now have into a switched 12v source, a good and easy one would be the power wire for the cigarette lighter and it is easy to get to.
Ground the single ground wire you now have into any good ground, an easy one is the mounting plate for the shifter under the surround and all that junk.
Run the purple (I believe that's what the autometer one is) wire for the O2 sensor source out through a gromet in the firewall, I found enough to use on the passenger side where the AC evaporator has its runoff tube go through. Then tap that into the O2 sensor wire running from the O2 sensor to the harness.
You're done.

 

Don't connect the signal wire at the sensor, you will most likely regret it. Connect it at the ECU, where you can also get switched power and ground (refer to the FSM wiring diagram). The cigarette lighter is the easiest place to tap into an illumination wire.

 

whilst on this subject - mine came with an o2 sensor for the exhaust

should i get that welded into the exhaust or use the on thats already in there ??

and mine only had 3 wires - red / black / purple

would the stock 02 sensor give out the correct reading for the a/f unit - or is that why it came with its own ??

and why would we regret tapping into the 02 unit on the exhaust ?

Ta

Stu

 

right then the O2 sensor is located on plug 2C on the ECU

and it says

IDLE : Below 1.0v
ACCELERATION : 0.5v - 1.0v
DECELERATION - 0v - 0.4v

so unless im missing something - how does that tell you if you are running rich or not ?

 

Replace the old sensor with the new sensor.

Power, ground and signal respectively.

All 0-1V narrow-band sensors work the same and give the same result. The new sensor will work better because it's not gummed up with 15 years of exhaust residue.

Because the wire in the engine bay is shielded. The shield wire is grounded. If you tap into this wire you will most probably contact the shield wire as well, sending the O2 signal to ground. Both the ECU and gauge will then get no signal. The last part of the wire near the ECU is not shielded, so there is no risk of this happening.

Stoiciometric is at ~0.5V. Below that is leaner than stoiciometric (which you will see during deceleration), above that is richer than stoiciometric (which you will see during acceleration).

 

how many wires did the automete a/f gauge come with? i just pulled mine out of a parts car, not sure if it's got all the wires or not

 

well mine came with 3 - does that help !

NZConvertable - thanks for that - very helpful !

did i get the ECU pin right ??

 

 

hmm- <right click- save as> ^^^

 

this is a bit off topic - BUT

when you look at the wiring for the S5 ECU - are all the pins on one plug - or is it split into a few plugs ??

 

Both S4 and S5 ECU's have three plugs, hence the numbers. I should've split the plugs in the pic.

 

ah right ! - thanks for that !

and we can tell which is which as they are all different sizes !!

superb - another project for when i get the car on the road again

thanks for all your help

stu