GMC Envoy, dashboard gauges not working. Started with the gas gauge, then the battery, then the temperature, not the RPM. It seems like the gauges don't reset (or return to zero) when ignition is shut off. Then when you restart, they start up at the position they were left at. Example: Temperature gauge remained at 100 when ignition was turned off. When I started the next morning it began at 100 and rose to over 200 making it seem as if I was overheating.

This appears to be a follow up of a question I answered earlier. Posting follow ups here doesn't work because each question has no context the the others. You must have deleted the earlier one or you posted anonymously.

According to this, only the 2002 model had an oil temperature sensor.

https://www.google.com/search?q=2005+gmc+envoy+oil+temperature+sensor+location

Your best bet would be to download a manual so you are sure what this gauge ACTUALLY is. HERE it is

https://www.manualslib.com/manual/61408/Gmc-2005-Gmc-Envoy.html?page=167#manual

Top row: Oil Pressure - Battery Volts
Bottom row: Fuel Tank Level - Coolant Temperature

..

scan the ECT if it reads wrong most time the 17 year old thermostat is bad. stuck open, missing or those crazy fail safe stat gone wild.
ect 180 to 200f is normal .
if not thermostat is first. I used and IR gun to measure the stat hosing to see if its bad, 1minutes work,
most times the gauge never fails so we do 1simple test to prove that.
scan the PCM is first.

never seen a STaT good 17 year old,
had one that told near all day to hit 180f>?
when old that do nasty things, even stick closed and warp HEADS
why risk that, attack the stat.

It's probably your speed sensors or your whole speedometer cluster

You need to test the dimmer switch. Remove the switch and check for power to and thru the switch

Most likely stepper motors that 'drive' the gauge needles. I've recently replace 3 on my 04 Envoy. fairly simple fix if you're a little mechanically inclined and decent with a soldering iron. save yourself a TON versus dealer service. Google GM Stepper motor replacement for a bunch of info

if the gauge runs at this point under normal driving conditions consider it to be normal for that gauge,temperature gauges vary from vehicle to vehicle, if it fluctuates too much you may have a problem but if it is constant there is no need to worry.....hope this helps.....cheers.

you need a new cluster if you have less than 75,000 miles check with the dealer gmc issued a recall for that, if your over that look on ebay for a replace or repair service

That is a manufacturing defect associated with your instrument cluster. My local dealer replaced my entire instrument cluster for free (truck was out of warranty) when my speedometer showed 100 mph in a parking lot and my oil pressure gauge read 0.

It sounds like you have an earth problem. Check for security and cleanliness of the earth points from the battery and the earth cable from the chassis to the engine or gearbox. hope this helps

VOLTAGE REGULATOR
Located behind the instrument cluster
It is attached to the rear panel of the cluster.
input from battery is 10Volts, it regulates down to 5Volts
Any higher voltage inputed will overload the capacitors and resistors will burn,
Also check power distribution center, under hood upper motor area in drivers corner, check all relays and fuses.
Before you rip in to the dash check all ground wires, battery to ground, harness grounds, driver/passenger mid fram rail, Fuel sender is also ground to top of gas tank. IF ALL gauges do not work, that just leaves voltage regulator and/or cluster is malfunction,