'Service Engine soon' warning light

Thank you gentlemen for advice on 'Coolant' question.
I am employed at local college, which has ' a state of the art' department. Car manufacturers donate to us many brand new vehicles (some dammaged during transport to dealers). The students therefore have the latest models to learn on.
I have already printed out your advice (the check with voltmeter for acid content in coolant). I am sure they will appreciate it. I have ask them about the gummy, brown deposit in filler neck and their response was '....O, yeah, the Del Cool coolant is no good...' Change it.
My car has now 37.000 K on odometer, the collant appears to be clean, reddish color. Before I posted my question here, I contacted the delaer and they (obviously) wanted to make an appointment for Rad flush etc..Sating that they have now a 'a Special' on this for $ 79.00 (Canadian). I will have them do it or have the rad flush and refill here at the college.
I thank you very much again for those words of comfort. I am very happy with the car (comfort, pick up, fuel economy etc..) The only thing that is annoying is the quite complicated programming of the door locks, lights etc..
I have another question, but I will post it in new Thread...
Greetings from Canada
Peter Solarik