Hello, everyone! I've got an 04 blazer, RWD, 57k miles.

My gas gauge has recently become a little bit optimistic, reading about 1/4 tank over my actual tank. But here's the weird thing- when I plug my OB2 scanner in, it suddenly snaps to the correct value! It also tends to drift more towards the correct value (As determined by odometer and filling the tank) once the engine has warmed up after driving for a while.

The only other thing I see is that when I start the truck when cold, the voltmeter also reads a bit high, and settles back to 14v after a while of driving. Voltmeter also wiggles a slightly when using the turn signal.

I'm going to try cleaning the engine grounds this weekend, as if I recall correctly, the fuel sender grounds to the back of the engine on the passenger side? It almost seems like the OB2 scanner is providing a better ground path for the fuel gauge when plugged in, but I'm still trying to figure out if that grounds to a different spot or not. But if anyone else has any ideas, let me know! And of course, I'll report back this weekend.

 

So... a little update:

I managed to poke around a little bit over the weekend. Mostly cleaning a couple of grounds. The gas gauge is currently reading about 2-3 gallons over what I actually have in my tank... but at least it's now consistent instead of being a bit jumpy.

I'm going to do a little reading up on the fuel sender, but it seems to me that there's currently just some extra resistance in a wire that results in a higher fuel reading. First I have to verify if the sender reads 0 ohms at empty or full, then I'll go measure the fuel sender ohms. These are the fun "issues" to solve: I learn more about how things work, and it has zero impact on drivability.

Looks like the next thing on my list is replacing some O2 sensors on my folks' Suburban, though, so sorry optimistic-but-now-consistent gas gauge, you'll have to wait a bit longer.

Happy blazing!