There is always the VF workshop manual in PDF form. Admittedly it takes a while to learn how the manual is structures and where things are so one can manually navigate the broken links but it’s worth getting as it will provide most of what you need and more…
In fact the sensor schematics on page 4789 only shows a single 2 wire engine coolant temperature sensor connected to ECU for LFW/LFX. The cylinder head assembly view on page 5604 shows the engine coolant temp sensor is located on passenger side bank towards the front for the LFX/LFW. I havent checked the actual location as I dont have an LFX/LFW
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See the following post #9 for a link to a free copy of the workshop manual
https://forums.justcommodores.com.au/threads/genuine-gm-service-manuals.265174/post-2903791
Really, if you are having coolant temperature issues, you need to compare what the ECU sees with independant measurements you make. Then check wiring and sensor performance as appropriate. Obviously if the sensor is determined as the thing thats faulty you'd change the sensor but if its a wiring issues youd fix the wiring. The diagnostics trouble codes (DTC's) can give hints where the problem may be but you need to diagnose and confirm
In the past diagnosis was more easily done by removing parts and testing them as things were very analog. Unfortunately these days the problem seems to be that some mechanics seem to have forgotten how to diagnose and/or use a separate independent devices (like a thermometer) to check what the car’s ECU sees (actual temp) is indeed within correct limits (as measured by the thermometer). Seems the strategy these days is primarily ECU driven DTC parts canon approach. Sadly it's too common an occurance where the owner find the fault remains after paying for the new parts, often because the fault is not the sensor but some wiring or module issue that wasn't correctly diagnosed
So read the workshop manual and understand how the VF coolant system works and how to diagnose problems as that will be helpful.
Once you’re satisfied that the coolant sensor is reading correctly and fans turn on in a staged fashion as expected, yet you still have issues, then you need to go further into a diagnosis (which the workshop manual goes into)…
Keep in mind that mecahniocal issues can influense cooling system performance, For example if you have a lot of leaf matter stuck in front of the aircon condenser or between aircon condenser and coolant radiator, air won’t flow nicely through the coolant radiator and coolant system will misbehave and overheat. In older cars with iron block, alloy head and brass radiator, often the radiator internal passages would fill up with rust matter and such blockages due to poor maintenance and in essence reduce the radiator surface cooling area yet because of [packaging you could place your hands on the radiator surface and feel the cool spots wee the internal passages were cblocked. Good luck doing that with a modern car. Such internal blockages are less of an issue when everything is alloy but who knows what condition things are in… Still, in such cases you’d expect to see the coolant system get hotter quicker… not stay cold as you're experiancing…
Also keep in mind that if the pressure cap isn’t performing as required due to worn or smooshed cap o-ring or aftermarket cap or damahed coolant cap sealing surface, the coolant pressure may not build as expected and thus coolant can’t carry away as much heat… which is why you check the radiator sealing surface where the cap is fitted and buy a new factory cap… Generally a sweet smell around the car/cabin indicates a coolant leak so you need to find it and checking the cap is the first thing. Again the coolant should get hotter quicker with a faulty cap, not stay cold as you are experiancing.
But this then brings up the issue of how you actually have determined the cooling system isn;t getting hot? Id it through independant temp measurements, using the HVAC heater and not getting heat or something else?
At the end of the day if airflow through the radiator is ok and pressure cap is ok and the electronics are working as expected, then the issue may be old style mechanical where the thermostat is intermittently sticking. Anything intermittent = PITA but a stuck open thermostat will result in the cooling system taking longer for the coolant to reach operating temperature... but it will reach operating temperature by virtue of the combusion occuring within the engine...
Just not ethat if you have low coolant so the temp sensor isn’t covered in coolant, the ECU will see low temps even though the vehicle may be overheating, so alwasy check for correct coolant levels while ensuring all air is fully bled from the system... Else you may damage the engine from unwittingly overheating. is important.
In all older car I’ve owned, I just replace the thermostat as it’s cheap and easy… But on a Holden v6 it’s a PITA to remove and replace the thermostat so its expensive which makes people reluctant to do what should be done… Still, if you’ve done everything else (checked sensor, sensor wiring and CAN coolant temp data* is all correct and also checked cap sealing surface arent scratched or marked and that colant opressure is building in the radiator hoses) then you may need to bite the bullet and just replace the potentially intermittent sticking thermostat
* hint: i'd be checking can data and ensureing the coolant temp is indeed logical. Youd think that in the morning after a cold 15C night, the can data should show 15C coolant temps at first start and it should slowly increase from there. At 82C the fans shold kick in and progressively get faster as temps increase further. If can data doesnt seem logical, then check sensor wiring at ECU and go from there...
