i am not sure if this is total coincidence, but once i installed the rtek into the car the BELTS light comes on when i start to rev/idle up the engine, and the STOP LAMP light comes on when i hit the brake. Belts seem ok from what i can tell and all the brake and tail lamps are lighting up. i think the display is still working because the ADD COOLANT light and buzzer were definitely spot on when i had a coolant leak. does the rtek do anything different with or interfere with the display?

 

-Check ground connections near the ecu and/or any wiring that you may have disturbed.

-Check the wiring harness for any wires pulled out of the ECU connecter that may have been damaged while removing the harness from the ECU.

-Make sure ECU is bolted down properly.

Basically what I am saying is that the car is decades old and probably more sensitive to grounding issues. Personally I had no issues when installing my rtek 1.7 or eventual 2.0. But, my seatbelt light does go on and off based on temperature/humidity/gremlins. GL.