SL/R129: warning light issue
sometimes the electrical wiring near the tank is a starting place, other times fuse /buss quality of contact can be an issue.
With your newer model the CEL can stay on after an event the CPU doesn't approve until the code is cleared.
The list of "un-approved" ( that sets a code ) events is long but noteworthy. If you are new to the OBD II diagnosis it is a curse and wonderful benefit, but way beyond my expertise.
good luck with you Benz






