Wiring AFR gauge, WHICH wire on O2 sensor is the "Signal" wire ?

 

There are 2 black, one white, and one blue wire....

Does anyone know which is the signal wire?

 

First, do you have JTIS printed? Do you realize the schematics are in there? The schematics show different wire colors from what you describe, AND they show a balanced input, so you need to figure out which two wires are the signal and how to connect your gauge. I would not get the balanced inputs tied to ground if I were you.

BTW, the colors you gave look like those on an AJ26 engine, which neither of the cars in your signature should have. Very strange! The black wires are the heater.

 

I have no experience with A/F gauges but I'd be a little careful tying into the signal routed to the ECU.

Those are fairly sensitive circuits that are looking for pretty small voltage and current shifts, so if your gauge pulls it too far one way or the other, you might have bad things happen.

If it's information you are looking for, have you thought about an Ultragauge? It is an OBD2 multi-gauge that can display a lot of information, including the O2 sensor output that the ECU is seeing.

 

My JTIS is not co operating. The only pages I can open say it has o2 sensors, where they are located, but no schematics...

So it is either the white or the blue......i'm going to guess blue... but wait to hook it up until I have the real info.

 

I think the ultragauge only updates 1x per second, I would like much faster updating than that, especially for a AFR reading.

 

The wiring diagrams are available separately as a PDF from the captainjaguar site. There should be a link in one of the stickies.

The wiring diagrams in JTIS are actually PDF as well, JTIS just links to the files in the folder. So, you could open up explorer in the JTIS directory and take a look for them.

 

In thinking about the microvolt situation, i'm going to avoid potentially messing up the signal, so I may go another route with this.
I'll do a bit more research, right now it appears welding in an additional bung and using a gauge the uses its own senser would be a safer route.
So for now I will just use the dyno data and circle back on this later when I have more info.

 

Yeah, your reference to "either white or blue" shows you do not understand my statement that it was a balanced line signal. You should google that and understand what it means before you give any consideration to making a single connection to it.
And BTW, the voltage level is millivolts, not microvolts.

 

What I understand is that my afr gauge says "connect to the signal wire" and shows a single wire to the O2 sensor.

What I also understand is the O2 sensor signal is sensitive as it gets it's readings in the 1/1000th of a volt range.

So, when I put these two together, I understand in order to avoid a serious problem, I should leave the stock signal alone, and if I want a real afr gauge, the best way is to use a system with it's own independent O2 sensor OR if I am ok with a 1x/second update rate, then use a guage that taps into the ECUs reading of the stock sensor. The later is sounding like the best option. Wouldn't you agree?

 

Ah Hah!

My OBDII driven ScanGauge II can be programmed to display the AFR via programming it as an "X-gauge"

Big

It only updates 2x/second, but that is enough to tell me if I am ok or in a trouble area, which is all I really need.

Problem solved.

 

Yes, I agree. Either of your alternate approaches seem mo better.

 

You would want to use a wideband O2 sensor to read AFR's, not the narrowband that the OEM most likely is.

Here's a simple explanation of the difference between the two:

Auto Meter

 

+1

Wideband and good quality o2 sensor, just read the kb site about it.

 

Here is a video of my ScanGauge II unit showing what looks like wideband: he floors it around 40 seconds into the video where is reads the AFR down to 10.9


Given I already have the ScanGaugeII, I will try it out to see if it is wide band on the Jag or not. If not, then I would definitely not rely on it.

When I do a dyno, I'll get a datalog of the continuous AFR, and the injector pulse width/duty cycle usage.

I just don't want to go too lean and have the sort of serious acute problems that can come from that.

My mods are not that wild, and my power level without the NOS is not that high, so I'm not too worried at the moment, probably well within what the stock ECU can adjust for, I just wanted the info to make sure all is well.

When I do use the NOS, I can adjust the fuel and NOS independently so I can fine tune AFR somewhat that way.

 

I do appreciate your looking out for me.

 

I am still wondering why you have the wire colors for an AJ26 engine on your AJ 27 car. I checked my MY99 (AJ26) and it has the colors you have, not the red /yellow that the AJ27 is supposed to have.

 

I have no idea. The door sticker says the car was made 2/00