rstarkie

1999 z28 6 speed 54K

Took this car to a tuner and he found a fault with the passenger's side O2 sensor.

He said that the O2 sensor was not letting the system go into closed loop. It was going to the default voltage that will let the car continue to run, but not adjust to readings made by the O2 sensor.

When I put the long tube headers on the car I had to extend the wires on the sensors. I did this using butt connectors and used heat shrink and tape on the connections.

I plan to renew the (eight) barrel connections in case the fault lies there. I would like to be able to check the sensor for function after reinstallation and before a return to the tuner.

I am unfamiliar with four wire O2 sensors. I assume there is a way to check the sensor with the engine running using a multimeter. Can someone direct me to a method to do this.

If the car needs a new sensor of course that is fine but I hate to toss a perfectly good sensor just because of a sketchy connection.

Thanks for any insight in testing the sensor with a multimeter.

Randy

rstarkie

Additional information:

I was able to find that the purple wire was the feed to the ECU. I was able to attach my meter to that wire and to ground and got the following-

I started the car and while at idle I initially saw a voltage fluctuation of .396v to .443v

After about a minute of idle time the flucuation increased from .350v to .660v

Somewhere around two minutes of idle the RPM's dropped to the warm idle level and the voltage immediately dropped to .187v before starting to fluctuate between .275v and
.776 volts.

I realize I should have checked with the meter before renewing all the connections but I did not. It would appear that the O2 sensor is working. The question has to be is the problem of not going to closed loop solved?

Is it possible for the sensor to function properly and just not get hot enough to go to closed loop? My understanding that once it decides to go to default it will not check back to see if conditions are such that it can finally go to closed loop.

I would really like to be sure that the system is going into closed loop before I go back to the tuner and embara$$ myself.

Thanks for any help on this.

EDIT: I went back and checked the heater wires (brown). These results are with the car running. The first one I checked just gave me trace voltage to ground (.43v); this turned out to be the ground wire as the other brown wire gave me 13.6v to ground. When I checked for continuity between the brown wires I got 6.7ohms. I would have thought both wires would have shown battery voltage to ground and continuity between the two brown wires.

Electrons and their behavior are pretty much a mystery to me... can someone interpret my data and tell if perhaps the heater element is bad in this O2 sensor. Wouldn't that account for it not going to closed loop even though the sensor itself is working?

Randy

01Z28M6

I have the same results with my checking and AFAIK you have the correct colors per function. The ground does seem to carry a slight voltage and this is what had me confused for a while.

My wide band sensor seems to work for a bit but I've come to believe that it quits simulating the narrow band (I have the Innovate LM-1 controller) switching when it gets to a certain high temperature. It appears to hold to a full rich condition of about .970 mv and this sets the MIL.

So, perhaps your connection is fine and the sensor seems to work but not after it gets good and hot.

BTW, I'm not too sure about this but you need to take care with a continuity test as it applies slight voltage to a very sensitive device.