I recently removed the battery from my 2001 cadillac catera and after that there were problems. The sunroof no longer opens and the car has a low idle and the oil pressure indicator light went on and off. Would this be linked to taking the battery out, or is it a fuse?

most likely an electrical problem.

first check fuse if fuse okay see if power going to control switch if yes the sunroof motor could be faulty or in a bind.if no power going to control switch, more likely if fuse good wiring from fuse box to control switch has short or broke ground or poor ground wire.

I had the same problem, it ended up being that the Body Control Module was water damaged due to a leak in the drainage hoses from the sunroof.

This and other details can find it in 2001 Cadillac Catera - Owners Manual.

Hope this helped (remember comment and rated this).

Check or replace/repair the K134 multi function relay module located under and up the dash on drivers side. Its about the size of a pack of cigarettes and gray in color.

I opened mine and re-soldered all the components on the board. I had radio going on and off, trunk not opening, sunroof with mind of it's own, and dying battery.

All was solved with this module...under $100 at the dealer if you don't want to goof with it.

You need to remove the upper rad hose and the battery.
Then, use a torx to remove the 6 screws (hard to get at) which will remove the EBTCM from the brake modulator. You also must disconnect the two electrical connectors (the big one has a slide tab).
There are places you can send the module to and rebuild with warranty. I took a module from a 99' and installed it in my wife's 01'. Now the speedo, odometer, cruise and power steering work perfect and no TCM / ABS light.

does it attempt to close at all?

There are 2 screws which hold the large panel right under the steering column. They use a large flat head screwdriver and are 1/4 turn. They are right on the bottom edge of this padded panel. The panel, which your knees should almost touch when sitting in the driver's seat, needs to be lifted up (slide it) after removing the screws as it is keyhole pinned.
The fuses are under there....there are more next to the battery as well.

Did you recently have a loss of power to the car? change the battery? if so, you need to reset your system. My husband and I just figured this out this weekend. His sunroof hasn't worked in two years and it turns out you have to reset all the power options in the car. Google 2000 cadillac catera %calibrate ETC% loss of power, you'll find the step by step instructions for recalibrating the car's computer and resetting the power options

ok your cable for the speedometer,odometer may be broken is the radio stock or aftermarket