re-wiring primary O2 (repost from electronics)
 

Got 0 answers in Electronics, so I'm trying here as well

The car had unichip installed and some wires were cut to install it. The unichip is not on the car, and the wires were soldered, however I have a problem with the primary O2 sensor.
After diagnostics/haynes manual, it seems I have to "repair open in wire" between ECU and O2 sensor.

Instead of taking the wire harness out, could I just take out the O2 sensor wires from the ecu and O2 socket and replace each of them with another wire?
Anyone know the length of the wires I need to use, or if the length of the wires affects anything?

Re-wiring O2's can be tricky since they put out a certain voltage to the ecu, which represents an AFR number. Thicker/thinner wire, weaker grounds, weak connections can all cause the voltage to be slightly different at the ecu thus causing an incorrect AFR reading.
Aftermarket ECU's (flashpro etc) are able to calibrate the voltage readings to whatever AFR you choose. Stock ECU's are not.
Just make sure you use the same gauge wire as stock, and about the same length (whatever length reaches from the ecu to O2 should be fine)
Stock O2 sensor really just reads "lean" or "rich" instead of the full scale. Widebands are 0-5v (with about 3v usually being 14.7) whereas stock O2's are something like 0-1v (with about 0.5v being 14.7).
Worst case scenario is that your voltage will be slightly lower, causing the ecu to think it is running rich and cutting back some fuel. Since the ECU only reads from the O2 in closed loop (partial throttle cruising and idle) its not that big of a deal to run a little leaner since there's not much load on the engine. At about 70%+ throttle, it will bypass the O2 anyway.

Runnig a bit lean should not be a problem, as i have the f20c2 engine+ stock ecu and i hear they run a bit rich from the factory.
Thanks!

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