VS V6 Poor Fuel Consumption - help analysing EFILive V4 data or suggestions

[VS Omega]

Hi everybody,

My wifes VS has some very poor fuel consumption (around 18L / 100km). I get the feeling it may be the o2 sensor/s because this seems to be an extremely common thing, so I played around with EFILive and noticed that there's a discrepency in the data from the left and right o2 sensors.

Straight up I had no idea there were two o2 sensors, only the one in the intake pipe. I guess they should be showing the same reading but maybe not if they're in different locations. I noticed while revving or driving that one will show a strong reading (900) while the other is lower (700), and it seems to alternate between the two sensors which one has more and which one has less. I noticed some times it even hits 0 for a second then goes back up. What's the chances the sensor's are stuffed, or is this normal behaviour and they're both working fine? Where's the other sensor?!

I've attached some screenshots straight from the program, don't know how helpful they'll be though they may help show what I mean.

Also any suggestions about using EFILive to diagnose fuel consumption problems, like which views I should be using in the "dashboard" or looking out for in the other tabs like DTC or status flags (sorry for asking but it's hard to find specific information regarding fuel consumption, efilive and vs commodores lol).

Many thanks for all suggestions and comments posted

[cander24]

There are 2 O2 sensors in an Ecotec V6 and they are located in the exhaust system primary pipes just infront of the catalytic converter (i.e. one screwed into each pipe). There is electrical wires connected to them.

[burnsy150]

Have a buzz through this thread

Code 76 + bad fuel economy = dead o2 sensor?
and also check out the link in post #8

with some luck should answer your questions

[Cheap6]

Straight up I had no idea there were two o2 sensors, only the one in the intake pipe. I guess they should be showing the same reading but maybe not if they're in different locations. I noticed while revving or driving that one will show a strong reading (900) while the other is lower (700), and it seems to alternate between the two sensors which one has more and which one has less. I noticed some times it even hits 0 for a second then goes back up. What's the chances the sensor's are stuffed, or is this normal behaviour and they're both working fine? Where's the other sensor?

In addition to the link and earlier comments:

On average both sensors should read the same at around 450mV, maybe 500mV. While cruising i.e. not idling, accelerating hard nor backing off, both will vary as the PCM continually corrects and over shoots rich-lean and back.

You should see the sensors go to high voltage and stop oscillating when you accelerate hard. You might see the sensors both drop low when coasting. At idle, they should oscillate for 20-30 secs, then go to slightly high of the 450mV.

You should also be aware that what you see on the screen is not necessarily what the sensors are doing in real time. The data for the program is only available at the rate at which the PCM transmits it and then EFILive processes it. The sample rate may be slow enough to miss some transitions in the O2 sensor voltages.

[VS Omega]

There are 2 O2 sensors in an Ecotec V6 and they are located in the exhaust system primary pipes just infront of the catalytic converter (i.e. one screwed into each pipe). There is electrical wires connected to them.

That makes a lot of sense about why they don't read the same - they're in different locations (I would have thought both in the intake)

Have a buzz through this thread

Code 76 + bad fuel economy = dead o2 sensor?
and also check out the link in post #8

with some luck should answer your questions

I looked at the pdf document in post 8, so if I understand this right I need to get the multimeter out and check the voltage on the two pins mentioned to see if they're the same or different, and if they're different it could be because of the earth not being correct and needing to be redone/fixed? If so any ideas how to check those pins (is it going to be one of those cables in the passenger side kick panel), like run the car and see what it is or the engine doesn't need to be running just in the engaged position (key to position before starter)?

In addition to the link and earlier comments:

On average both sensors should read the same at around 450mV, maybe 500mV. While cruising i.e. not idling, accelerating hard nor backing off, both will vary as the PCM continually corrects and over shoots rich-lean and back.

You should see the sensors go to high voltage and stop oscillating when you accelerate hard. You might see the sensors both drop low when coasting. At idle, they should oscillate for 20-30 secs, then go to slightly high of the 450mV.

You should also be aware that what you see on the screen is not necessarily what the sensors are doing in real time. The data for the program is only available at the rate at which the PCM transmits it and then EFILive processes it. The sample rate may be slow enough to miss some transitions in the O2 sensor voltages.

The behavior you've described seems to be about the same as what it's doing which is a bit reassuring, I'll go stick the cable/notebook in my car and do the exact same thing to compare.


Basically though, from the fact that the sensors are giving a reading would it be safe to rule out the o2 sensor as the culprit in this instance? Or might it help to swap the o2 sensors in both cars for a couple of weeks and see what happens?

Also does anyone know what "O2 missing=true" in DTC means?

Many thanks all

[VS_Pete_1]

Mate that pdf document that I found can`t be a ecotec motor it has to be a buick motor. Have a look at it you can see the Alternator at the top of the pic. On the ecotec it is on the other side of the motor.
Plus I had a look for the two points showen and I wear glassers but I`m not blind I can`t
find them.
I think they are at the ECU.