No... But it increases fuel consumption
more then likely you have a bad head gasket , or some other leak.
Coolant sensors can cause a lot of various problems. The ECM relies on the coolant sensor for temperature readings. This is so that it can adjust the timing, fuel, and other related systems. But without knowing more I couldn't say that it is your problem.
Serious. On the intake manifold a leak sucking in of air will cause a lean running condition generating excessive heat if the computer is unable to adjust by adding more gas to the mixture.
There's more than one cause of oil in engine coolant but the most common is a blown (failed) head gasket.
You must make sure that you have purged all air from the coolant system. An air bubble will not allow proper flow of coolant and could also cause the engine to overheat. Add coolant into resevior and leave top off with engine running. Add more coolant as required. If temp gets too high with cap off and coolant starts to back out of resevior, then replace cap and allow to cool. Remove cap after cool and top up coolant again and repeat procedure.
more likely to be a faulty coolant sensor or the thermostat is faulty and staying open
More than likely a blown head gasket or a cracked head.
IT means the engine is running lean. More Air than gas. And you need to be careful as it can cause t engine to overheat if the condition is sever enough.
The plastic coolant reservoir on the fender feeds directly into the coolant system. Just add coolant to the reservoir and if you have drained the coolant or otherwise emptied the system, you may need to check the level in the reservoir after running the engine, or more accurately, after the engine has cooled. Once the coolant level has stabilized, just check it periodically to make certain that the coolant level never gets too low.
That's okay in an emergency but you should also be concerned why the coolant is that low. Have a trusted mechanic check it out soon cause you may have a more serious problem going on.
Can be a hole in the radiator or a problem with one or more of the hoses. A mechanic can run a pressure test to see where the problem(s) are located at.
possibly a bad head gasket you might need more coolant