VZ ute/RA Rodeo O2 sensors and fuel economy

[gzerial]

My sons ute according to SOE diagnostic software is a VZ alloytec 3.6L V6 and drinks fuel to a point of disbelief. Ive read countless posts about the bad fuel economy and possible ways of improving it by way of replacing the O2 sensors. Unfortunately the ECU allows the diagnostics to only show the S2's or post cat sensors and not the pre cat sensors (S1). An A/F mixture meter put on the exhaust pipe and read very rich. So I replaced one of the S1 O2 sensors as they are relatively easy to get to. This seems to have improved the figures as the mixture meter now reads around the 14.7 mark ( stoichiometric) at idle. Based on this Im going to replace the other S1 sensor and probably the two S2 sensors to see if any further improvement can be made. If so the cost of the sensors will have paid for themselves very quickly based on the fuel useage he's getting. Im posting this in the hope that someone else out there can offer some help / advice / suggestions on improving this situation or have gone down this road themselves. I tried to include two jpg scans from SOE to show the difference before and after however at this point this new forum format wont allow it. Look forward to all responses....

 

[gzerial]

... and as you can see, I got around to being able to post the images

 

[gzerial]

View attachment 188612 ... and as you can see, I got around to being able to post the imagesView attachment 188612 View attachment 188613

So just to explain the above .. the first graph is the original scan I took before any work was done. The second is after I replaced the pre cat O2 sensor on the passenger side ... Im sure its Bank 1.
Anyway you can see its reading around the 800mV. Thats rich!. The second scan is reading around the 500mV which for a post cat O2 sensor is where it should be according to various posts.
So I ended up putting the O2 sensor that I replaced with a new one on the drivers side and immediately got an engine warning light.
Turns out the sensor is faulty. The following picture shows the difference between the two.
The left is the passenger side and the right the drivers side. The left showing now to be faulty.

 

[gzerial]

So now by all accounts the vehicle is running as it should and I wait for fuel figures to come back over the next few weeks.

What was wrong with the O2 sensor ?? If you follow the following it will describe how to test a 5wire Bosch O2 sensor:
https://www.picoauto.com/library/automotive-guided-tests/bosch-lsu-4.2-broadband-oxygen-sensor
The interesting bit is the resistance tests. Between pins 2 and 6 I was getting a reading of around 200ohms when it should be around the 100ohms region. This is the calibration resistor that is crucial for proper operation of the sensor. It can be fixed and Ive included a pic below showing where and what Ive done to replace the faulty resistor

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[Fu Manchu]

Big ups for posting this. Even though no one has replied, it's great to see the the work you have done to try nut this out. Many will be grateful for it