It’s very likely you have at least two distinct things going on here. While it’s not uncommon for the contents of a car’s radiator to appear murky or dirty, that’s not usually something that would trigger a check engine light. If the radiator is filled with tap water (not a good thing) then it can soon become rusty and dirty to the eye. It will still cool the engine, but you’re much better off with the correct type and grade of coolant to protect the engine from corrosion.

As far as the check engine light goes, you could be looking at literally hundreds of causes for this. The check engine light is telling you that something is not quite right and that you should have the car scanned at a workshop. That way, the computer can tell the mechanic exactly what’s going on and what needs to be checked, repaired or replaced. Until you do that, you’re effectively flying blind.

People often complain about the complexities of modern cars, but the ability to plug a diagnostic probe into a car and have the vehicle tell you what’s wrong with it is, indeed, worthwhile progress.

The two holes near the bottom of the dipstick are your Low and Full markers. If the oil is below the Low marker (the bottom-most hole) then you need to add oil. If the oil level is above the Full marker hole, then the engine has too much oil in it.

It’s pretty important to keep the oil level between the two holes. If you do that, you’ll be doing the engine a big favour. Too little oil can damage internal components, while too much oil can blow seals, contaminate the engine’s intake system or create oil leaks.

It remains a mystery to some of us why car makers ever switched from the old-fashioned manual levers for four-wheel-drive engagement to the rotary dial or electronic switch type. Pretty much everybody who has owned a 4X4 with the electronic engagement will have experienced a situation where the electronics just don’t seem to want to select four-wheel-drive when they should. This is usually a momentary problem, put right by trying the dial or switch a second time, but it’s still annoying.

Your problem is likely to be a poor electrical contact in either the selector dial or the actuators under the car that physically engage four-wheel-drive and/or low ratio. A quick check under the vehicle might expose a loose wire or broken fitting, but otherwise, a trip to a workshop that knows this make and model is your best bet. The good news is that the problem should be pretty quick, easy and cheap to fix once it’s been identified.