The sl-600 is much more troublesome than the 500 and 320 regarding wiring issues for two reasons. 1) there is lots more engine compartment heat which causes the wire insulation to fail sooner, and 2) There is a lot more wiring that has to work perfectly.

The main engine compartment wiring harness is very prone to failure from disintegrating insulation. The part cost is up to about $1700 or so. If the foam insulation inside the coax cable buried in the harness should compact or deteriorate where the cable turns a tight bend--presto-limp mode --the EGAS modules can no longer read the engine RPM from the ignition module (all the way on the other side, other end of the engine compartment) and so shut down as a safety measure. The MBZ electronic throttle is by far the least likely to have a 'runaway' or uncomanded acceleration type failure. Unfortunately, the converse is true--its the most likely to fail to work.