What does a 600 reading from the computer of a 2004 chevy trailblazer mean?

Have a diagram that shows 1-5-3-6-2-4 as firing order Firing order for 2004 chevy trailblazer 2004 Chevrolet TrailBlazer

no- no recall on the fuel tank that cracks at the filler neck the following link are complaints about fuel tank that are recieved if you go to home page and enter trailblazer they give you the break down of the whole series of model and complaints as well as recall information they also list the TSB technical service bulletins
2004 Chevrolet Trailblazer Crack In Fuel Tank

A jet engine type of noise from the engine area usually means the fan clutch is going bad. I don't think the tach is related to this, that could be the stepper motor for the tach going bad.

If you're saying that the RPM's are too low (less than 600), you need to clean the throttle body. Make sure to clean v=both the front side and rear side thoroughly. Also, disconnect the battery while doing the cleaning, this will reset the computer and allow it to relearn to the newly cleaned throttle body.

You may have a oil pressure switch going bad or your idle is too low. The idle should be around 600 RPM. The oil pressure displayed on the instrument panel gauge is not an actual reading, it is made up by the computer. You probably should clean the throttle body as well, make sure to clean both front side and rear side thoroughly. Also disconnect the battery while doing the cleaning. This will allow the computer to reset and relearn.

You sure you don't mean camshaft position sensor? Yes this is readily available everywhere.

yes

You want heat up ????? Not clear if you want heat higher on the engine or cabin. Engine, you should probably leave it alone. The manufacturer warns that running higher temp thermostat may cause overheating damage to engine. If you want heat up in cabin, by nature and design there is a limit to how much heat is put out. Colder days it simply may not provide a sultry 85 degrees, if that is what you mean when you say "you want the heat to go up". Maybe try wearing a jacket.

try changing the air filter ,i had a problem ,at ilde in drive my trailblazer would stall, changed the air filter now it's not stalling and got my power back ,there is a secondary air pump that i have to change ,
not sure were it is ? still not running perfect but it's running better .and my service light is on too.
i got it put on scope ,it's the pump .
not sure if this helps ,but i'm start to run in to problems too,i have a 2004 trailblazer.
i like to do fix things myself ,i hope i can.it's the cost if you know what i mean.

your relay is going bad, replace it.