Couple of points:

A voltage lebel of .4 to .5 is an O2 sensors normal operating range.

The O2 sensor is a voltage generator based on heat and chemicals. If the O2 sensor is dead, it isn't going to generate a voltage level. Also note the error description that was reported in the first post ie "output voltage constantly lower than 0.04 V " ie BELOW the lowest measurable voltage.

The O2 sensor is technically not an output sensor - it is an INPUT to the FI system thus the term loop ie the system reacts to the O2 - not the other way around.

While a techinical description of the O2 is fun, I wasn't suggesting that this WAS the source of the problem only that it would be very easy to confirm or not if the O2 sensor was bad by flipping them between sides since a single nut holds them in place.

-mick

Si Lambo, the symptoms you describe are exactly what it feels like on one bank of cylinders. Doesn't want to start as it should, doesnt want to rev as it should, no power, doesn't run especially rough. Needs loads of throttle to not stall on moving off.

Mick, the normal operating range of the Lambda probe is not 0.4volts. The probe output fluctuates between 0.2 to 0.9 volts during closed loop operation. If the sensor is inactive then the output voltage gets stuck at 0.4 volts, and this throws the "lambda sensor inactive " error code. If you put a multimeter across the probes, you can see how the voltage fluctuates.

I'm talking about the voltage from the wire on its own out of the three to each sensor, relative to ground. Perhaps we're at crossed purposes ???


In my experience a bad lambda sensor does not produce anything like the symptoms that Si is describing, my car has no cats and I've driven around with a bad sensor, it really doesn't make a massive difference.

An output voltage of .45 indicates not rich or not lean. The system tries to maintain this value. Fluctuations (cross counts) above and below this value indicates a normal and good system.

Let me try it this way, if the O2 sensor is removed from the system, the sensor cannot be generating a voltage of .4 into the system. It would be zero and the error stated in the first post is what you get.

I guess its possible. I'm specifically talking about the OUTPUT of the O2 sensor. It sounds like you referencing the bias voltage that some FI systems send TO the O2 sensor.

-mick

Mick. agreed if there was 0 volts, this could trick the computer into throwing a code 2 error. When lambda sensors go bad and become inactive, the voltage across them is steady at about .4 to .5 volts regardless of what is going on with the exhaust gases.

I had an O2 sensor fail recently and this is exactly what happened.

Are you saying that the lambda sensors also fail and throw poor mixture error codes ?? It's an important point, because if my car throws a code 2 error, and I measure a low votage across the Lambda sensor, the last place I am going to start looking for the problem is the sensor itself.


regards
Mike

I agree however, by using a simple measurement at the O2 connection you are mixing voltage output from the O2 sensor and the bias voltage added by the FI system. The typical bias voltage (if present) is .45 volts ie if the sensor is removed you will still get .45 across the connection. The ECU, obviously aware of this bias voltage will logically subtract it out and conclude that the O2 sensor itself is not adding anything to the equation ie is producing zero volts and report it bad - code 2.

In my previous postings, I focused on what voltage is produced by the O2 sensor itself (which is what the ECU is reporting) and not what voltage may or may not be present at the connection.

But to backup to what I view as a simple trouble shooting step, if the engine is firing and the exhaust manifold has reach normal temps and the ECU is reporting that the O2 sensor is bad, then taking advantage of the fact that a DIABLO has two O2 sensors by simply unscrewing them and flipping them is 15 minutes of work to either confirm or discount the sensor being bad and requires nothing more than a wrench.

My D Roadster had a bad O2 sensor but worse it was intermittent. Flipping sensors was a very cheap and quick way to confirm the part failure. A failed O2 sensor on a Diablo (especially older ones) is not a unique problem.

-mick

I really hate to end this thread. I learned much more than I bargained for, however I resolved the issue.

Thanks for everyone's input

Evans Automotive diagnosed the problem right out of the box. George said it sounded like something was disconnected after I hit the pot-hole and asked me to first check the coil wires. (Now why didn't I just look under the hood?)
Bam! All I had to do was look and saw the wire hanging on the air box. The connection was corroded and broke.

I just repaired the connector and I'm back in business.

Attached Images

Coil wire broke 10 05 2006.JPG (25.1 KB, 26 views)

Good news, hopefully we all learn a little bit from your experience.