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There have been some misleading recommendations regarding the correct ECU pin to use for the A/F gauge floating around lately. I received the correct STi ECU pinout sheet from Dan at godspeed.com today (THANKS, Dan). The correct ECU pin wire to use is connector B137, terminal #25. It is a white wire. It is NOT B136, #26 (this is the signal terminal for the FRONT O2 sensor). The correct terminal is for the REAR O2 sensor signal, not the front O2 sensor. The front O2 sensor reads in a very wide voltage range (which most A/F gauges can't read- short of the EXPENSIVE wide band gauges) while the rear O2 sensor reads 0-0.9 V (which the more commonly seen A/F gauges display). This also makes the cheapo A/F gauges completely worthless, as the gas being monitored is quite a ways downstream. The computer only uses this rear O2 sensor signal to monitor cat-converter efficiency, while the front O2 sensor reading is used to adjust A/F ratio. In essence, the signal from the rear O2 sensor only serves to light up the pretty LEDs in the gauge rather than provide any useful information. Either way, I hooked up my Autometer A/F gauge because I had an open spot in my gauge housing and figured the gauge looked better in the vacant spot of the housing than it did sitting idle on my garage floor. Let me know if anyone wants a copy of the ECU pinout.
 

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Re: custom interior... like or no like?

gesundlich said:
There have been some misleading recommendations regarding the correct ECU pin to use for the A/F gauge floating around lately. I received the correct STi ECU pinout sheet from Dan at godspeed.com today (THANKS, Dan). The correct ECU pin wire to use is connector B137, terminal #25. It is a white wire. It is NOT B136, #26 (this is the signal terminal for the TGV). The correct terminal is for the REAR O2 sensor signal, not the front O2 sensor. The front O2 sensor reads in a very wide voltage range (which most A/F gauges can't read- short of the EXPENSIVE wide band gauges) while the rear O2 sensor reads 0-0.9 V (which the more commonly seen A/F gauges display). This also makes the cheapo A/F gauges completely worthless, as the gas being monitored is quite a ways downstream. The computer only uses this rear O2 sensor signal to monitor cat-converter efficiency, while the front O2 sensor reading is used to adjust A/F ratio. In essence, the signal from the rear O2 sensor only serves to light up the pretty LEDs in the gauge rather than provide any useful information. Either way, I hooked up my Autometer A/F gauge because I had an open spot in my gauge housing and figured the gauge looked better in the vacant spot of the housing than it did sitting idle on my garage floor. Let me know if anyone wants a copy of the ECU pinout.
Thanks for the info - on my list of things to do/buy.

-st
 

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Re: jammers

Here are the pinouts:

http://www.phear7imports.net/subs/btroop/trey/STi/files/05.%20Engine%20Control%20Module%20(ECM)%20I-O%20Signal.pdf

Toggle to page 2 then back to page 1 to see the plugs......
 

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ok this is a stupid question but where is the stock ecu located? passenger side?
 

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gesundlich,

Thanks for info.

- Where/how do I access connector b137 terminal 25, the white wire? I am assuming this is a plug that goes into the ECU? I would like to know how to access that.

- My gauge is a Defi-D-guage Air/Fuel. It's a needle sweep with numbers not a blinking light type. I have a heated narrow band sensor that mathces the gauge. I easily can weld a bung to attach my guage sensor in the exhast pipe at the transmission area where the "cat-back" part of the exhaust begins.

- WIll this work better than tapping into the stock rear sensor at b137 terminal 25? Where is that stock rear sensor? Is your point above that the stock rear sensor is too far back in the exhaust system so it is not accurate?

- Like you, I want to use my gauge as I have spot for it and can't afford anymore stuff right now. Which of the two ways to attach it above is best.

- Any help on acccessin the ECU connectors is appreciated as well.
 

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Sorry if this is off topic.I was thinking about getting a defi a/f gauge ( D-gauge). Is is it pointless to have it?

Greg
 

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This is great, thanks. :D
 
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