Thread: Regrounding the O2 Sensor

Hey scotty what do you think of routing the ground strait to the battery's negative terminal? would this provide a better path?

Nope.. Much worse..

That was one of the first places we tried... The battery ground is actually grounded on the block. Thus, completely different reading than the Intake Mani... Block grounds provided the 2nd worse readings, followed closely by the 3rd worse grounds to body parts (inside of the fender or wheel well; even with the paint removed)..
The absolute worse grounding connection found was to the Stainless Steel Exhaust Mani (home of our 3-wire O2 sensor)!!!

My guess is that the battery ground cable is so large that the quality of that ground connection is improved due to the size of the battery cable & surface connection size..

Believe me guys, we have tried many places and none were the same or as good as the Intake Mani..
Thats why every other sensor & the ECU is grounded there too..

Update: See Post 359 below

Would there be a problem using the harness from the 3 wire 02 sensor.

It can be done using a 3-wire or 4-wire harness.

With the 3-wire harness, we use the universal O2 kit and wire in the 3-wire plug from the old O2 sensor. Then, we add the 4th grounding wire to the universal O2 ground wire. At the plug connection point, we use a torpedo plug connection for the ground wire and the 3-wire connections for everything else. Then from ground wire connection, the new ground wire is routed and connected to one of the Intake Mani grounding screws near the firewall.

With the 4-wire connector, we source a 4-wire connection from the junkyard; cutting the 4-wire O2 connector plug & the engine harness connection. Using the new Universal O2 sensor, we wire up the 4-wire O2 plug. Then we cut the engine harness and wire up the 3 wires to the 4-wire connector (triple checking the wires). The 4th grounding wire connection is wired to a new ground wire and is routed & connected to one of the Intake Mani grounding screws near the firewall using a quality ring connector.

Both methods will work. The second method is more work, more likely to cross wires, and requires cutting the engine harness (a definite no-no). So, we recommend the first option.

Hope this helps..

Thanks I'm trying to do this right now LOL Thanks for the fast response.

Heres a picture of mine using the 3 wire connector:



All of the O2 wires should be the same size.. I used a larger gauge for the ground wire to makeup for the distance to the Intake Mani..

Heres a closeup pic:



Heres the engine harness setup:

^Wow DC. You must be in a good mood today lol.

Yada, yada...

Another forum member posted this excellent description for MAF/ECU grounding principles but the same principles applies to the ECU and all of the engine sensors (IACV, Knock, MAF, O2, Temp, etc):



I have tested some battery grounds and the reading was -13v to -14.2
This is makes an even larger negative difference with the Intake Mani ground readings.
The quality of the ground connections are just as important as the power connections.

Summary
So please dont be lazy and use the battery ground for this O2 sensor ground mod or the MAF ground mod.
Both will be adversely impacted and your resulting mod may even make these sensors respond worse...

The ECU is grounded on the Intake Mani screw with all other engine sensors except for the O2 sensor. The MAF harness ground over time looses its strength/accuracy by sharing its ground connection with other sensors (inside the main harness). By adding additional ground to the MAF & creating a new ground for O2 sensors directly to the same surface/grounding plane as the ECU, the signal for both sensors improve dramatically.

^Great post DC. +rep.