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Old 10-18-2004, 11:33 AM   #1
Scooby Guru
Member#: 24956
Join Date: Sep 2002
Chapter/Region: MAIC
Location: Littlestown PA
1997 Impreza WRX
Steel Blue Mica

Default Blue wire mod

What this is, for anyone using the SAFC, is a way to read your O2 sensor voltage.

On the SAFC harness, you have 2 wires for your MAFs, or whatever your input signal is. You have 2 because some cars have 2 MAFS, ie. Skyline TT. So your extra wire gets tapped into the O2 sensor, and on your sensor check on the SAFC you can see the voltage coming from the sensor. The only downside to this is the SAFC puts a load on the sensor and can modify the signal to read up to .06 volts less than what it is.

What I'm wondering is, what should the sensor efficiently be reading? I looked on my ECU pinout and it says .70 volts is rich, but that seems low. Some websites said closer to .98 volts. Am I correct in assuming that the higher voltage means rich?

Also, this isn't quite an accurate tuning tool. It just gives you a general idea, which is better than no idea at all.

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Old 10-18-2004, 12:16 PM   #2
Scooby Specialist
Member#: 1197
Join Date: Apr 2000
Chapter/Region: MWSOC
Location: Cedar Rapids, Iowa
1997 Impreza Wagon
Mystic Blue Pearl


This link might prove helpful.


Conventional oxygen sensors work more like a rich/lean "switch" than as a measuring tool. At anything other than light throttle, they're virtually worthless.

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