Thread: Regrounding the O2 Sensor

And you should kinda know how to fake out the Rear one

The 15727 is the downstream O2 sensor which would be after the cat, 15726 is the upstream O2 sensor. The 15727 is the Planar style so is that still the one to use? Would there be a difference in the readings?

Use 15727 for front ONLY. This is what the Bosch representative told DC Scotty.

15726 is a 3 wire O2 sensor, it's no good

I figured you guys knew what was going on. Rock auto must have things wrong then. Here is the page i found.
Thanks again for your help, i will order the 15727 and be done with it.

Well technically the 15727 is for the Rear, even as per Bosch's website when you look up a 1999 Sentra 2.0.

Since our cars were designed to use 3 wire sensors, for plug and play reasons no site will tell you to use a 4 wire up front

All True...

The correct ODBI & ODBII universal front O2 sensor is 15726. The correct ODBII universal rear 02 sensor is 15727.
The 15726 is a 3-wire and the 15727 is a 4-wire.

The only equivalent 4-wire for the 15726 is the 15727 (signal is exactly the same) according to the Bosch technician. The 15727 O2 sensor was developed to support manufacturers with Stainless Steel Cat/Exhaust due to the very low grounding properties.

Thus, all of us with 3-wire front O2 sensors AND Stainless Steel Headers will regain the lost grounding properties by switching to the 4-wire 15727 sensor. This will produce a stronger sensor signal and a more accurated O2 sensor reading. With the 4-wire sensor, connect the new grounding wire to the intake mani for the best results.. Gains should be seen in Gas Mileage and smoother idle. Dont forget to reset the ECU after installation.

FYI: One other note, going with a aftermarket vendor with true boxed Bosch sensors is the way to-go ! ! ! We have found that although the Ebay vendors are much cheaper, the O2 sensors sold cannot be verified as the correct O2 sensor. The ebay sensors do not have the appropriate stamped ids to determine the O2 model. Thus, go with Summit, Rock or other vendor with the BOXed Bosch part (w/the Partno on the box).

Ok so that makes sense. Thank you for clarifying this. So rock auto is correct about front and rear but both are NOT 4-wire as stated.

So then what front o2 sensor should I use on the SSAC headers... I'm lost now. Sorry

Wayne your such a noob

I posted this a while back on the front page, but 15727, you can get one fairly cheap at here. Rock Auto also has them

Why are you lost?? What dont you understand??
SENTRIXX IS NOT A NOOB ! ! !

Stainless Steel does not provide a good ground.
The 3-wire O2 uses the Exhaust Header as the grounding surface causing weak/slow signals to the ECU if the Header is Stainless Steel.

If you have Stainless Steel Headers (SSAC is Stainless Steel :rolleyes,
You can Replace your front 3-wire O2 sensor with the Bosch 15727 Universal O2 Sensor (4-wire).
Then, you can Connect the new 4th grounding wire to one of the grounding screws on the Intake Manifold..

Your new O2 sensor will use the ground from the Intake Mani which is also the ground location for the
ECU, TPS, IACV, Air Regulator, and most other engine sensors.

The New O2 sensor will now:
- Send a stronger signal to the ECU (due to the better ground)
- the Signal will be more Accurate & faster (Planar technology)
- the O2 will heatup faster than the older O2 (improved Planar O2 heater)

Hopefully, this explains it better.
And hopefully this will improve your gas mileage and idle.
(and if we are lucky...... maybe help resolve some bogging @ low rpm).

Lastly, post your findings here for everyone to share the information!!

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