O2 ?

[lionelhutz]

The sensing element in the O2 sensor is NOT isolated!!!

http://www.ti.com/lit/ds/symlink/lm9044.pdf

Page 1 clearly shows grounding the negative side at the sensor. The sensors have the connection. I have tested it. Do I need to take a picture of the ohm meter reading to prove the connection exists in a sensor?

Of course grounding the negative lead creates a path to ground. The lead is connected to ground for crying out loud.

But that should not be confused with claiming it screws up the chip, because the chip is designed with the expectation that the negative lead will be grounded.

The use of a 1, 3 or 4 wire O2 is rather irrelevant to the IC used inside the PCM. How many cast case PCM's with the lambda IC didn't use a 4-wire O2?

If you are going to use a 4-wire O2 then why leave the wiring with 2 separate connections to the engine or transmission or exhaust? Just avoid any possible connection issues and connect the O2 sensor wires right to the ECU/PCM and be done with it.

If you are going to leave connections to the engine block then you might as well stick with a 3-wire sensor.