2006 Chevy Trailblazer ext

So I'm stumped. My SUV gets warm and every
single traffic light or slow traffic I hit, the oil
pressure gauge drops down to 0, the check gauges
light comes on, and the dash tells me to stop the
engine. I brought it to the shop and they cleaned
the throttle body and replaced the oil sensor. Now
it's still acting this way, just a tad less. My
mechanic told me the next step is to replace the
entire throttle body. UGH He can't figure it out so he
thinks changing that may do it. Any ideas or
anyone experience this and gotten it fixed?