I have an 89 5.7 GTA, and I've been having a problem with the car not going into / staying in closed loop. O2 is new AC delco heated. While datalogging (using TTS Datamaster) O2 will almost always read 444. Occasionally it will have healthy xcounts, but usually only when driving hard then it goes back to 444/open loop. (this is with the car running for over an hour)

I had trouble reading the voltage on the sensor - I really wasn't sure how (read it connected, disconnected, and meter settings) But, there is continuity from the ECU D7 (o2 signal wire) to the O2. I also tried grounding the signal wire while datalogging - no change. I expected that to cause the 444 to go to 0 but it did not.

I'd hate to keep buying sensors and ECUs. I am leaning toward replacing the recently purchased AC Delco O2 but I am not sure that is the problem.

Any opinions?

 

'addict

Where do you measure ECM voltage????

ECM supplies 450 mV bias voltage while NBO pushes and pulls against as exhaust O2 concentration changes. A cold NBO will stay at 450 mV as it requires to be heated to about 600F - reason for a heater circuit. When you drive hard the exhaust system gets heated hot enough to bring NBO up to its operating temperature. Check your heater circuit - get a DVM measure current consumed by NBO heater. Cold NBO should draw 2 to 4Amps from 12VDc and drop down to about 1Amp as it warms up.

//RF

 

Does it go hot enoght to be ready ?
And what reading to you got if you unlug the signalcable (o2sensor) and measure with an ohm/voltmeter ?

Is it the same or do you got other values then ?

 

FYI: It's been a while but I finally got it -
I cut the tan wire and attached it to the body and instantly saw the O2 swinging - thanks for the help