I bought a 1994 Cadillac sls last week and I notice my car is not shifting gears
It was shifting out of 1st gear but now it keep just going fast but not shifting and my engine light is on. No transmission leaks please tell me it just a sensor

 

Need to pull the codes to determine the problem....or at least what the computer thinks is the problem.
With the key ON, press and Hold the OFF and WARMER buttons on the climate control panel until the information display lights up all of the lights. Then, just copy down the codes that show on the information display, and post them here. You may simply have a bad speed sensor, or it could be something much more complicated. The earlier(93-94) 4T80E transmissions had an issue with a screen/filter blowing out of the valve body, and breaking one of the shift solenoids. GM came out with an update to correct this, that involved replacing the solenoids and filter screen, and installing a bracket to keep the filter from popping out of the valve body. There's a good chance that this is your problem, but it's also possible that this update has already been done.
We need to know the code before we can go any deeper into it...
hth

 

P029
p052
p076
p109
p086
i052
t072

 

P029 = Shift Solenoid "A" problem
p052 = Keep alive memory reset(did you disconnect the battery?)
p076 = Pressure control solenoid(EPC) circuit
p109 = Keep alive memory reset(did you disconnect the battery?)
p086 = Undefined gear ratio

Chances are, your solenoid is broken from the filter/screen blowing out. You would need to remove the bottom trans pan to see/fix this.
The Gear ratio code is due to the trans not shifting. Once the shifting problem is corrected, the ratio code will also be solved.

The EPC solenoid circuit code might be valid, or it might be due to the filter blowing out. The EPC is in the SIDE cover of the trans...not the bottom, as the shift solenoids are. Removing the side cover to get to the solenoid in the car is a MAJOR pita, but it has been done. For us, it's easier to remove the complete trans.
I would suggest you start with pulling the bottom pan off, and inspecting for a broken solenoid. If it is broken the lower valve body will need to be removed and disassembled to replace the solenoid, and install the updated bracket to hold the filter/screen in.
If you remove the lower pan, and the solenoid is NOT broken, then you have an internal trans problem, and it will need to be removed and repaired.
I hope it is just the shift solenoid. The early cars, 93-93 did NOT have the bracket to hold the filter/screen in in, but most have already been updated by now. Yours might have survived way longer than most. How many miles does this car have on it?

 

124,973

 

It may have already had the update, with that many miles. Most won't go more than 50 thou or so without the screen blowing out, but ya never know. Still worth looking at it to see for sure.
I think I posted a pic here somewhere of the lower VB w/solenoids, but I may not have. I'll look and see....