92 Blazer S10 gauge issues
 

My speedometer, odometer, trip odometer, and voltage meter all work, but my oil pressure meter, gas gauge, and temperature gauge do not work. I have checked and tested all fuses, but that does not seem to be the problem.

Gauges are analog. Service engine soon light is on. Check gauges light goes on intermittently.

I bought the car fairly recently - the gauges have never worked since I have been in possession of the car. The previous owner installed a new stereo system, and I suspect that they may have screwed up the wiring when they did so.

Any ideas?

possible if they cut the ground wire or spliced into it.

there was a problem with the older 80s blazers where the gauges would become all screwy, in the case of those there was a small ground wire that screwed upwards into the dash right at the bottom front corner of the dash and it would come loose.

i dont know if your truck is too new for it to have the ground wire there but its worth a quick check, just stick your head under there and should be like a 1/4 inch bolt going upward in the left corner of the dash

Gauge cluster has a printed circuit board, it does not take much to disrupt the connection at connector. I would advise removing and cleaning the connection with an abrasive like Emory cloth.