Cadillac Repair: check ingion light, climate control, crusin

Question
1988 caddy devilli check light comes on when crusin at 30mph and 40mph the car will purge ate thoe speeds the check light come on flashing. try code readeer put flash to fast cannot read the code. tride jumping whit wire the lite still flashes to fast can not read the code.  What code reader should be use       I will buy it. help/

Answer
1. Ignition switch ON. engine OFF.

2. Simultaneously push and hold the OFF and WARMER buttons on your climate control panel for 3 seconds and release them.

3. Diagnostic codes will start to appear and display will stop at .7.0

4. Tell me EXACTLY what CODES display on the screen as if you were video taping it.

5. Turn ignition off.