Have seen this happen before but was under unusual circumstances. Was at a location where another tech was performing maintanence on a lift and it done as you described. Checked unit and found wire broken on lpg pressure sensor and smoke was due to not removing dipstick when filling crankcase with oil. Comfirmed this by removing PCV hose from valve cover and finding oil in it. After talking with service guy found he had not let oil have time to drain in oil pan before starting engine. Wire was broken due to wire connection checks. Repaired wire, cleaned out remaining oil in hose and cleared code. Smoked for several minutes and cleared up.