Hello has your check engine light come on because the transmission will also have fault codes stored on the computer's memory so you will need a diagnostic to find out the failure code and system problem.HAVE A BLESS DAY from DR.RECO
RepairPal Certified shops can diagnose and repair your 1999 BMW 323i. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.