I have a 95 900SE Turbo which was checked by a Saab garage after the Check Engine light was coming on. The fault was identified as a
faulty Lambda sensor. I've replaced that but the light is still on. I disconnected the battery, is there a reset switch or something which needs altering? I'll be grateful for any ideas.

The check engine light will usually reset itself after a period of time provided the cause is rectified. This may take several days or weeks depending on the amount of use the car gets.