What does code P0502 mean - 2001 Cadillac DeVille

P0xxx codes apply to all vehicles using the OBD2 system, P1xxx codes are manufacturer specific. Your codes mean...

P0753 = Shift Solenoid "A" Electrical.
P0502 = Vehicle Speed Sensor "A" Circuit Low.

This is possibly 2 separate issues as one is a transmission fault code and the other is a vehicle speed sensor issue. Get the speed sensor repaired first as sometimes the bad signal from the sensor can confuse the transmission electronics causing the transmission to behave strangely.

Vehicle Speed Sensor (VSS) circuit low input.

Check out this link
P0502 Saturn Vehicle Speed Sensor Circuit Low Input

This is what I found for the code. P0502

call any auto part store.. I called Auto Zone they read them all off to me...now best of luck YOU got a P1870 ???

That is a speed sensor "a" low input code. Sometimes the sensors are external and sometimes they are internal. I don't remember specifically for your vehicle.

I would suggest monitoring the sensor with a higher end scan tool capable of reading transmission data.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

check all fuses to start with. then check all grounding points... for that many codes usually means a bad pcm or loose ground wire..

P0302Cylinder 2 Misfire Detected for the P0502 click on this site or plug it into your address bar.
http://engine-codes.com/P0502.html

P0502 Vehicle Speed Sensor "A" Circuit Low Input

Change the speed sensor or check the wiring to it.

The Code you're referring to should be a "P0502." What the Code signifies is: "Vehicle speed sensor circuit, low input."

P0404 Exhaust Gas Recirculation Circuit Range/Performance
P0502 Vehicle Speed Sensor Low Input
P0440 Evaporative Emission Control System Malfunction
hope that helps /a little beyond my expertise but theres your codes your looking for ;)