2000 Nissan Maxima

SLP warning light…car has traction control system that is an on again off again problem. I took the car into dealer for service and they could not trouble shoot problem. The warning light has been coming on for past 18 months. When light is on car runs rough and shakes. Does not seem to be engine related or transmission.I think it may have something to do with traction control system. The problem is recurring but does not last. Any ideas

You may find a mechanic at an independent shop. There should be codes set in one of the computers which would help the mechanic.
The Traction Control System may be affected with the engine problem.