After the brake warning light went on, the braking system has been serviced. The mechanic found one of the rear brake cylinder leaking and replaced it. The braking system was bled off and checked on a special device that checks braking power of each wheel separately and found working perfectly.
However, the warning light won't go off. Can it be a combination valve problem? when i remove the connector from it, the light goes off.
Should it be replaced or can it be reset somehow?

Thanks.