I have a 2003 La Sabre Limited with 120,000 miles. Service stability light comes on constantly.
Codes: C1287..steering sensor rate malfunction
C1288...steering sensor circuit malfunction
Pin point test diagnosed a bad electronic control module.
Anyone know if this sounds correct?

Could be either the EBCM or the steering wheel position sensor. A malfunction of either one will trip the SSS light. With those codes I would normally suspect the SWPS. What is this "pin point test" you refer to that indicates it is the EBCM?

By the way, if you do have to buy an EBCM, contact the guys at Morad. I bought a used one from them for a heck of a lot less than a new one would cost, and it works great.

The mechanic just wrote that he performed pin point tests..........

To answer your original question, yes, a malfuntioning EBCM can definitely set the SSS light on. I don't know what these pin point tests are, but if we rely on your mechanic, the next step is to change the EBCM. If you are at all handy, and have some basic tools, it is one of the easiest repairs you can do on your car. Remove a couple of things to get at the EBCM, undo the electrical connector, remove a few attaching screws, then reverse the process. The EBCM is on the "dry" side of the brake system, meaning there is no brake fluid in it, meaning no mess and you don't have to bleed the system when you are done. As I stated in an earlier post, the best place I know to buy a used (but good) EBCM is from Morad. Do a google for Morad Car Parts. Send them an email with your vehicle'* VIN and they will be able to determine what the correct replacement part is. If they don't have the part in stock, they will tell you the part number, and suggest one or two other places that might have it in stock.

If you are not comfortable doing the work yourself, I would buy the used EBCM and pay your mechanic to install it.