I am retired from25 yrs as aoto tech. I used to enter diagnostics on Caddis by pushing off and warmer at same time. will a 97 deville work with same procedures through the AC controls? Family member has one with starting problem. good cranking speed, just delayed ignition majority of time with occaisional service engine light. from a glance, the AC controls are quite different than what I remembered.

On most models, you turn the key switch on but don't start the engine. Push "off" and "warm" to enter the diagnostics program.
When 70 appears on the fuel screen, push "off" and "high fan" at the same time and hold until all symbols and numbers appear, then release.

GM's batteries are worthless try an auto parts store most will do diagnostics for free i would say your alternator is intermittent they can load test it to find out

E52=memory (history) has been lost.try ERASE all your codes and see if any come back.1.turn Ignition ON, Engine OFF.2. Push and hold the OFF and WARMER buttons until all the segments on the display illuminate and as soon as the codes start to appear, Push the OFF and HI buttons and release them until you see .7.0.
3. Turn ignition OFF.

use a highr grade petrol ,this vehicle was not designed for unleaded and as such has no cat so maybe a lead additive (europe) if it does have a cat then the timing needs retarding a bit to 6? as this age will have a distributor .

came across this, maybe this will help out...this is for analog gauges....

With the ignition in the "RUN" position (engine does not necessarily need to be running, but it will work either way).
Press OFF and WARMER (or the OFF and PASSENGER WARMER buttons) on climate control panel simultaneously. Instrument Panel Cluster (IPC) will light all telltales, then go blank. System is now in DIAGNOSTIC MODE. After diagnostic mode cycles through and stops, press FAN DOWN button until "RFA?" is displayed, then press FAN UP. If "RFA DATA?" is displayed, press FAN DOWN. If "RFA OVERRIDE?" is displayed press FAN UP button.

If "RFA S00 NO OVERRIDE" is displayed, press FAN DOWN. If "RFA S01 PROGRAM FOB #1" is displayed, press FAN UP button.

IPC will show "0" on right side of Drivers Information Center (DIC) display. Press WARMER button on the climate control unit until "99" is displayed.

Press and hold TRUNK button on the transmitter. While holding TRUNK button, press LOCK button and hold both buttons for a total of 3 seconds. Locks will cycle when programming is complete. If transmitter is not programmed within 30 seconds after entering "99" on the display, system will default and you must begin at step #2 again.
To program second transmitter, press FAN DOWN button until "RF S02 PROGRAM FOB #2" is displayed, then press FAN UP. Repeat step #4.

To exit system, press AUTO, MODE UP, MODE DOWN, or RESET button.
__________________

key on engine off hold the off and warmer buttons at the same time all instrument lights will come on (wow effect) when they go off you are in PCM diag. but for obd2 systems you really need a scanner best to use a tech 2 (gm)

DID YOU SIMULTANEOUSLY PRESS THE OFF AND WARMER BUTTONS ON THE CLIMATE CONTROL PANEL.IF THIS DONT WORK TAKE CAR TO AUTO ZONE THEY WILL USE A SCANNER TO PULL UP THE TROUBLE CODE.THEY WILL DO IT FREE.

Turn the key on. Hold off and warmer on the climate control until all the lights light up. It will now read out all the codes in all the computers. Let it go until it reads (PCM?). Now push up on the blower speed. It will read PCM DATA. Now push down (I think 3 times) until it reads CLEAR CODES. Now push up on the blower speed. It should read PCM CODES CLEARED. Now turn the key off.

Hold down off and warmer on the temp control to put the car in self diagnostics. See if you can get airbag codes and you should be able to erase them using the fan up and down buttons.

My retired uncle has a 97 cadillac deville sts that runs well but after a short distance or time idling begins to overheat. He has replaced the water pump, thermostat and had the radiator and head gasket checked. Unfortunately he lives in a rural area and there is no local cadillac dealership for diagnostic repairs.