Flat lined 02 sensor

The rear o2's should not be switching/following the front o2's. If so the cats are not functioning or they are missing.

I like to see this stuff in graph form. Your first picture looks like a very slow sample rate.

So, still need to see a nice graph of all 4 o2's. Fuel trims, and what symptom is leading you to believe there is a problem.

 

He is getting bank 2 O2 sensor codes.

 

Yes, what codes specifically.

 

The refresh rate with that many PIDS is going to be slow. Not saying not to do it, just letting folks who actually understand how to read this stuff (not me) know that so they aren't mislead by the results.

 

Ok, so we are still at either a bad connection or bad sensor. Something is causing an open circuit. I'm not sure I would do this, but if you unplugged the sensor and shorted the ECU signal and ground wires together I would expect to see the 0.435V drop to 0V or close to it. If it did then that would tell you the ECU side of the wires are good and the sensor is definitely the problem. If it doesn't drop to zero then there is a bad connection or bad wire (open circuit) on the ECU side.

Or you could connect a old, weak 1.5 V battery between the ECU signal and ground wires and you should see the voltage rise to the battery voltage if the connections/wires are good. (Positive side to signal wire).

Or you could do the "battery touch test" as in the video but that would only tell you is the signal wire is good.

I can see you are enjoying yourself here, Bob.

 

I have Scan XL Standard. Cost a little more and probably didn't need it but it does a little more, not that I've ever used it. I can not see how anyone can make decisions on what to do w/o this kind of software. I wonder how many $1600 a pop plus labor "fixes" have been done to correct problems that would have easily been detected can simply corrected with $30 - $100 worth of software.

By the way, compared to our friend Dave up north, it's plain balmy around here at 35*F. May I'll go out in the Boxster with the top down today.

This is the problem with being retired in CT. It's hard to get motivated to do anything except waste time on the net when it's like this.

 

Going to the Hartford International car show this weekend. Jeanne want a new car. She's thinking about a Mercedes GLA.

 

Oh man thats my old stomping grounds. Tweed blvd just south of there was my favorite place to go fast, dropped my R5 turbo and 930 off the side several times LOL Lots of houses up there now, even the missile silo is gone now

 

Back in 1969 I was returning ti CT from visiting a college buddy still at Penn State. I 84 was not completed yet. I took 209 out of Stroudsburg PA north to US Rt 6 and then across Bear Mountain in my 1969 Z28 which just happen to have the diaphragm in the power break booster fail on the way home. I remember coming down the east side of the mountain with no power boost, standing on the brakes as hard as I could. This was a car with the JL8 4 wheel disk brake option and w/o power assist it was like dragging you feet to stop it. Haven't been back out that way for a while. I'll have to put it on my calendar for next summer.

 

You know I just remembered something, you said you have a 308, I remember in the early 80's many 81. I went up the NY Thruway got on just north of the Tappan zee at the first toll booth ran with a 308, and BMW I was in a red 930 to the Albany exit in 1 hour 03 min early one Saturday morning, I remember because a trooper was at the exit and was handed my toll ticket. I think 127 miles or so in an Hour 3 minutes. Good thing he was a car enthusiast and took my PBA card. I think they were waiting for me LOL

EDIT My memory may be off, may have been driving a white RX7 full GTU car, no decals with dealer plates

 

The cat stores and releases oxygen. The rear O2 voltages DO oscillate, just at a different (slower) rate from the fronts.

 

Yes I should have worded that differently. You are correct they will oscillate but they should not mirror the primary 02's.

 

Bob, It only took you 19 days!

 

I want to point out another thing here. I have read a lot about failed headers resulting in excess oxygen being entrained into the exhaust with the result that the car goes full rich with resulting engine damage. The thing is that if these is excesses oxygen in the exhaust driving the car rich you should be able to see that in either or both the O2 sensor and the term fuel trim. Excess oxygen, resulting in a lean condition, would drive the upstream sensor to a low voltage and the fuel trim to a high positive percentage, long term, short, or both. So while there may be numerous reasons for excessively rich fuel trim, bad MAF, vacuum leaks, burnt valves, bad O2 sensors, as well as exhaust leaks, I would expect that if the long and short term fuel trims are within normal ranges the headers are not in bad shape, or at least excess O2 is not being entrained into the exhaust through them. (Use this info at your own discretion.)

 

Agreed with all of the above post^^