Hi there. Thanks for the advice. O checked the plug and it was loose. The error messages are gone. As for the light I adjusted the switch and it's working now. Appreciate the advice and support

I have a 2002 S80 2.9 sedan. 141,000 miles.New Jersey, USA. I had a leaking brake booster, bought a used one, installed it and it is now working fine. After I was finished, the ABS, STC, check engine and brake light on the dashboard all came on, as well as and the brake lights on the back are on all...