Broken head gasket at back of engine - at #5 and #6 cylinder.
You may now find lube oil in the coolant and / or coolant in the lube
oil - a confirming symptom.
These straight sixes are known to break their head gaskets after about
150K miles. It could be from the differing coefficient of expansion of
the cast iron block vs. the all aluminum cylinderhead. Many cycles of
expansion and contraction in 150K miles - overheating also kills head
There's nothing else to do but remove the cylinderhead, check the head
and block for flatness and install a new gasket. Cost of ownership.
The signal on the dash may be totally unrelated and indicate worn brake
pads. Check your manual.