1996 K1500 Interior light / Tune up problems

My interior light will come on and stay on when it gets under 40 degress out- What can I do to stop this?

\Also I just gave my truck a tune up the service engine light came on and there is now a spark nock. I had it diod and they shut the light off but when I stepped into it the light came back and so did the spark nock. I changed the plugs, wires, distrubter, cap, rotor button and O2 senser. Anyone have any ideas?

Tim

What was the code from the service engine light?

Wixi

Check you door jam switches.

I had same problem when it got cold.