"sensor code indicates oil in the wiring harness"
That would ask for sensors sensing the wire harness for oil, these sensors
again need their harness but perhaps use the same sensors :-)

Please clarify, the issue must be on the harness, on the sensors, perhaps
oil sensor or something like that?

Yes, this is a known problem.  As one MB mechanic posted to a UK group, "The
camshaft adjuster leaks oil internally and this goes into the wiring loom
(harness). The oil travels along the loom and usually ends up at the lamda
sensor (O2) on the exhaust. If you're unlucky, it goes into the engine
ECU...more money! This can be avoided by fitting an in-line loom mod bit,
which is about 6" long and is designed to absorb oil and not let it pass
through to the loom... The problem is only on later 111 engines - very last
of the 202 c class, early 203 c class & 208 clks...Part number for the mod
is 2711502733 £14.36+vat. I would recommend anyone who has an early 203 4
cylinder with engine number starting 111 buys this part. It is an easy DIY
fit. Remove front engine cover trim & plug new loom between cam adjuster &
old loom. This may save you £1000+"

Doug

I’m right in the midst of this problem.  I’ve had both O2 sensors
replaced already, and it’s looking like both the wiring harness and
ECU  is next.