Question.....When headgaskets, EGR, injectors, etc. go bad or fail.....other than physical/visual signs, does any warning light (like a check engine light) come on?
An injector issue can cause a check engine light but not likely. When the head gaskets or EGR cooler go, usually no check engine light. Sometimes don't even notice a difference in the way it runs. However, you will get white smoke out of the exhaust and/or coolant puking out of the overflow.