Thread: Regrounding the O2 Sensor

Not to thread jack this thread anymore, I thought I would start a new one...

Here is some information that DC Scotty Stated in that thread, that got me thinking...






UPDATE

It seems like the best way to fix this is by going with a 4-wire Bosch Oxygen Sensor Part #15727

Wire diagram on how to wire up the 4-wire O2 sensor.

[ATTACH=CONFIG]919[/ATTACH]

Big thanks to DC Scotty for bringing this up, talking to Bosch/getting the right part numbers, and figuring the SSAC header gas mileage mystery!

just like regrounding the wrong wire on maf, it could fry the ecu.

Oh ouch, I'll keep that in mind

Now a coworker of mine suggested getting a dummy O2 sensor that would just constantly read 14:7 a/f ratio... what do you guys think?

EDIT: This would be pointless since it would run off the map only (which will have varying AFR's depending on the day and mods)

Hey guys.. Thanks for starting this new thread as we were jacking the other headlamp wire thread.

My objective is to gain better O2 sensor operation. My theory is that the ground on the Stainless Steel aftermarket header is not providing the necessary amount of grounding needed for the O2 signal to the ECU. Also that the signal to the ECU is weak and causing issues with gas mileage, bogging at low rpms and possible other idle issue. But, I can be completely wrong here!! But doing some test, I will attempt to verify if my theory is true or a contributing factor to some of these problems.

O2 sensor wires
I have purchased two (2) types O2 sensors: the OEM/Bosch thimble type sensor and the NGK planar type sensor. Both are constructed with 3 wires. Bosch also makes a 4-wire O2 sensor but not for the SR20DE motor (not sure of other motors).

The wire colors are different and Black does not mean Ground:

OEM 3-wire (Bosch Thimble type):
1. Black wire for the signal
2. Two (2) white wires for the heater.
3. No signal ground wire (ground is achieved through the sensor body where it threads into the exhaust system).

NGK 3-wire (planar type with square tip):
http://www.ngk.com/more_info.asp?AAIA=1211735&pid=4014
1. Blue wire for the signal
2. Two (2) Black wires for the heater.
3. No signal ground wire (ground is achieved through the sensor body where it threads into the exhaust system).

Bosch 4-wire (Bosch Thimble type):
1. Black wire for the signal
2. Gray wire for signal ground
3. Two (2) white wires for the heater.

Note: As you can see above - Not all O2 sensor wires are colored the same. You must determine the correct wires by reading the manufacturer documentation.

So now that we know that the Black wires ARE NOT ground in all the above cases, we can now see the problem. The 3-wire O2 sensor depends on external sources for grounding.

The 4-wire O2 sensor would be a great solution due to its signal ground wire. We could simply wire it to a good grounding position and work is done. I will contact tech support at Bosch to find out the possiblities of using a 4-wire sensor on the SR20 engine. Then, we could just replace our 3wire connector with a 4-wire connector and run a new wire from the signal ground pin to a good ground source.. Will keep you updated with an answer (if they respond).

But for now, we are stuck with the 3-wire connector. So, somehow we must improve the header ground properties.

Yesterday, I purchased a Napa grounding strap. I have began promising test by attaching the grounding straps at the header/downpipe joint using the connection bolts. I also tested the straps using the Cat bolts. Tonight, Im going to cut the strap and test connections at both locations.

I will post my results here..
.

Just a suggestion...

What about running a wire with large ring/semi-circle terminal to physically fit between the sensor and the downpipe/exhaust... I'm sure if it's the proper size it will seal correctly.

yep, but the wire will melt from the extreme heat..

Why would you want that? Your ECU bases some of its mixture adjustment off of the 02 sensor reading

Good Info DC Scotty!

You just stopped me from ruining one of the wires

Now I recently replaced my O2 sensor with a Bosch universal one. I still have my old one, I can strip it apart and see whats inside



Just getting a perfect reading at all times might get a good gas mileage, dunno about performance though hehe

Haha, only good mileage in the eyes of your ECU though. You could still be running way rich and the ECU would not know to lean it out.