Rpm meter not working

so what works and what not.
so far we have cluster issues
does car drive, ok day and night.
and all accessories?
did engine stall driving?
did Head lights dim? on, driving?
my guess is the engine stalled or idled below 300rpm
and the ECU went to Key on self test mode, (they all do that)
watch the RPM guage? see that needle, ?
if it goes below 300 rpm that is engine stall.
or worse
This cars cluster is really just a digital display
so if the PCM cant talk to the cluster, the cluster will go nuts.
for freeze.
We use a scan tool to see whats up.
or use the cluster self test covered in the shop manual.
the cluster has 2 fuses that can be cracked/loss or corroded.
the cars battery can go weak.
if the charge/battery light glows, engine RPM good
then the alternator systems is failing
if the volt meter (if opted) in cluster drops below 14v, and engine is still running, the same, alternator system failure
or even a loose belt at the alternator.
if the battery voltage drops too low , all electrics go nuts.
and engine stalls.
what dies first with low battery , is luck of the draw....
so what was battery voltage
and engine RPM at the point of failure.??????????

Chris i would suggest changing the cluster out i had a tach problem and that fixed it. As for the other things did it all happen at once?

This is a very common problem with the 03-06 Trailblazers and most other GMs. It's caused by the stepper motor that controls the gauge movement wearing out, it can be repaired however - check out this page for detail - Trailblazer Instrument Cluster Repair. If you are a DIY'r you might want to get this guide on how to do it yourself - http://howtorepairmyinstrumentcluster.com/

did you check the fuse?
that sounds more like the problem!!!

Pretty common problem with these. Here's a guide to learn how to fix GM instrument clusters yourself, I used it to fix mine and it worked great.How to guide for Silverado instrument cluster repair

This is an INSTRAMENT CLUSTER Problem, I Have Seen it Before,
Be Sure of IT's CONNECTION and if thats Not it Swap the Cluster.

look and see if you blew a fuse if not you'll have to remove the cluster and make sure it is plugged in if all this is right the cluster is possibly bad it happens.

I had the same problem with a car i owned and found out it was a short in the wireing in the dash, you will have too have it re-wired, but too be certain you should have it checked out by a mechanic in your city.........

well the issue is youe enitre gauge cluster i do understand that your speedometer is working but it is a cable speedometer not electronic like everything else in the gauge cluster so first i would recomend checking the voltage getting to your gauge cluster then just replace the guagecluster they are really cheap i a salvage and not hard to install at all but the cluster itself is not very comon to go out so make sure you check voltage to it first i wouldnt want you to go through buying and replaceing the cluster and that not fix it

If sender is new in the fuel tank, you have a wire problem between conection of fuel sender and dashboard gauge most likely place at dasbboard gauge.