It might have a needle and look like a gauge.. but it is a digital gauge. It is not directly connected to the sender. It connects to the ECM and is driven by a stepper motor through a digital interface that uses logic.. there is an actual temp range that will cause it to read dead center of the gauge.. and yes that engine still uses a thermostat but they are fading away.
FWIW I daily drive a ‘12 Sierra 1500 and also work as a GM technician so I’m very familiar. I don’t deal with anything older than GMT 900 in general but still do some with the 900’s
I was going to say much the same about temp gauges pointing where the ECU makes them point rather than pointing to actual temp on a lot of vehicles.
On a lot of modern vehicles the temp gauge will point to absolutely 'normal' temp shortly after engine start when the engine is still warming up from around 38C 100F and still be pointing to absolutely 'normal' temp if the engine gets up to 105C 220F.
On some modern vehicles the temp gauge does point to actual temperature but on most it works like we said.
I would much rather have an old skool proper temp gauge connected directly to the temp sensor than the type that has the ECU sitting in the middle telling the gauge where to point, too often when the ECU decides to let the driver know temp is unusually hot it's too late to prevent a worse overheating problem. Can't use such gauges to know there's a developing problem, it tells you after there is a problem.
I believe manufacturers started having the ECU tell the temp gauge where to point because consumers like to think their engine is quick to warm up then maintains exact normal temp regardless of conditions. Over here a lot of cars are front wheel drive so have electric cooling fans, the thermostat might be set to 85C 185F but the electric radiator fan won't come on until coolant temp is 105C 220F, to some drivers it would be alarming seeing the temp gauge point to normal while actually driving/moving but slowly climb to 220F if stood at traffic lights not moving for a while before slowly coming down again when the fan kicks in. If one manufacturer puts the ECU between sender and gauge and programs the gauge to point to normal at such a wide range of actual temps it could give consumers the idea they make the best engines unless other manufacturers follow suit.
My daily driver is a Nissan Elgrand JDM import with the VQ35 engine, I can start that on a freezing winter morning and within about 3 minutes the gauge is pointing to abosultely normal temperature but you can tell it's not really up to temp because the heater still doesn't blow as hot as it would if it were really up to temp and if I read coolant temp using OBD live data it's still only around 100F at that point. I've done a lot of work on the same model car and know the gauge will continue to point to normal until coolant temp is around 110C 230F, then it will start to read only slightly above normal., any hotter than that and the gauge will suddenly move to the far right but it's probably too late to try to start nursing it even if the gauge moves slightly further round than normal. My missus still has the same old car I bought her to learn to drive in, an old 2002 Vauxhall (GM), that does have a gauge that points to actual temp and it is a much more useful gauge. Start that up on the same winter morning and drive it around for the same 3 minutes and the gauge still hasn't started to move from the far left cold position, it reads 85C 185F in normal use but will go up to 95C 203F if parked up with the engine running before the fan kicks in..
My son's BMW doesn't have a coolant temp gauge on the dash (you can see a reading going through hidden menus), it does have an oil temp gauge on the dash. I used to like a full sets of gauges on old cars... coolant temp (with no ECU in the middle), oil pressure, oil temp, ammeter. Daughter's car recently had a failed oil pump, she was lucky it failed when she came to start it rather than fail while she was out on the road, there can't have been any oil pressur because I found the oil pump had broken up but if you started it the oil pressure light wouldn't come on for about 5 seconds after starting. I changed the oil pump on it for her and fitted a timing chain kit and water pump while I was at it, might as well on that engine because they're all consumables that are known to fail and all have to be removed during changing the oil pump anyway, front cover and all the timing stuff off plus the sump off. Pita doing it on her driveway.
