Service engine soon light came on. What type of service ie required? I left the car running on a hot day accidently for about 45 minutes. I had two hard starts before it caught several days ago but has been running smooth since. It is time for an oil change. I was thinking a tune-up and maybe having the transmission fluid changed. It never has been changed at 54K miles

Best use OBD II scanner,read the code and fix it.Sometimes to rest helps too.

You need a better code reader, ie "Mechanic". The ECM should control "Running rich or lean". Is engine light? Quote, Service SOON or Service NOW. SOON is usually minor, but needs to be found in the codes. "NOW" need to be checked immediately.

Take it to autozone or another place like it and have them read the codes and tell us what they are.

disconect battery wait 5 minutes reconect after 3rd time driveing light will reset itself

Always on,why is that?

Those thype of lights have been on all vehicles
for over 30 years as required by the govt in north
america at least,so how is it your not checking for codes
almost the same day you get a light on your dash

That is a MIL Lamp or Check Lamp indicating your car
has a possible faiure in one of it's many systems

You check for codes right away & diagnose,resolve or
repair within a week inless it isn't something that would
ruin your engine or trans etc.

The wording service soon is misleeding & nothing to
do with you getting some type of service at your convenience,
it is a serious problem untill you check for codes & at least
have some indication of the system effected

gas cap loose? could be mileage milestone light go to auto zone or advanced auto they'll read your codes for u for free

remove dog house locate test port and install guage should be 45-60 psi

Sometimes you have to wait a week for the light to go off, the computer has to go through several start/run/stop cycles.

I have the exact same problem it took awhile before I figured it out.This car requires the medium octane gasoline .The 87 octane gas causes the engine to run on the lean side and triggers the "service engine soon light".By putting in a higher octane gas (middle range 92 octane) the light won't come on.Or you can get your service mechanic to set a richer gas mix for your car,however you'll lose about 2-3 mpg .

The code that it is throwing is P0128, "Coolant Temp Below
Thermostat Regulating Temp. If your car is not running hot try this. If it is running hot take it to the shop or replace your thermostat yourself this is probably the problem.
Simply disconnect your battery, turn on the headlight switch for about five to ten minutes, and re-connect the battery. This is pretty simple, but will likely result in you losing your radio presets and perhaps some other small things like that.
This will reset your light. If it comes back on your thermostat or temper sensor may be bad.
Good Luck Hope this helps>