Issues following HG replacement and TB change -- Need troubleshooting help

[rdp2n]

I have just spent a month's worth of spare time replacing the headgaskets and timing belt on my sister-in-law's 2008 Subaru Outback (95K).
Along the way I replaced spark plugs, wires, all timing gear bearings (and both front axles & brakes for good measure).
I took my time, was careful, and was confident that the timing gear was installed properly.

Today, I recharged the battery, and reconnected everything, put in 4 quarts of penzzoil 5/30, over a gallon of subaru coolant diluted 1:1
I turned the key and the car started first time. Sounded fine at first. However, the check engine (CE) light was on and the engine speed
went up and down gently -- seemed to be "hunting". Then I went to the front of the car and as the engine warmed up (<2 minutes) smoke
emanated from the driver's side exhaust area. Turned the engine off. Looked underneath and could see nothing untoward.

Restarted the engine after 30 minutes and repeat performance ensued. Put in a bit more coolant along the way. At no time did the engine warm up properly.

Attempted to restart after another 30 minutes -- but this time, the engine coughed and died at startup. Now I have a no-start situation.
CE light on throughout. (Maybe I missed a sensor connection (?) -- or something silly -- but I was slow and careful -- don't see where ...)

 

I just accessed the DTC codes -- and I get a code of "P0198" with a description of "Oil Temperature Sensor Circuit Malfunction High" (would this be referring to engine oil or transmission oil?)

Can anyone suggest how I should proceed from here?

Thanks,


Rob