Not sure I want to see the federal mandate but I can see the general complaint about the check engine light being rather worthless. Unfortunately most people probably don't' know what most of their warnings actually mean. The other day I was riding with a coworker who said she needed to get an oil change. She indicated that the oil light had come on a few times. Upon telling her what the oil light normally indicates we checked the oil level and found the dip stick was oil free. I think I added a quart and a half to her 4 cylinder Hyundai. What good is a warning light if people don't understand the warning?

 

Many people don't even understand the difference between amber and red symbols, much less what the symbols actually mean.

If you've seen modern IPs you know there's plenty of room for simple messages that can outline check engine codes. It could be as simple as your gas cap is loose to your ERG valve is bad to you have no oil, stop driving immediately.

The point is, the message should be able to say two things - this is the problem, this is what you need to do about it.

 

Succintly put.

 

The only thing I would change is to add an idiot light that says "Tighten Gas Cap" in the case of evap canister codes. If people want to know anything about a car, they'll at least know/find out they can read the code/get the code read for free. The large majority of people still won't even want to know that.

On some models of cars (that have more advanced displays available and/or use a service like OnStar that has capabilities to communicate with the outside world/email diagnostic reports, etc), I could see building some better logic in anywhere from a basic display of a code and a suggestion of the urgency of taking it somewhere, maybe up to on emissions codes, being able to clear them a few times until a threshold is tripped in a given time range to where it would suggest that there is a problem worth taking a look at, etc. But I don't want that on every car/want it mandated.

 

So you want car manufacturers to spend money on something that will lose them money?

 

I think all that really needs to be done is to have some kind of standard that prevents basic issues (like the gas cap being loose) from displaying as a full-on 'Check Engine' light, but rather show some other indicator. There should be some kind of standardized definition of what is and is not an actual *engine* issue so that people can differentiate.

In the end though, it's up to the end user to educate themselves about the issue or pay the price for being ignorant/lazy/oblivious--as with anything else in life.

 

This.

 

The issue is that the codes are merely responses to out-of-spec readings from a sensor. The most common example in my experience is O2 sensor codes. They don't mean the O2 sensor is bad and needs replacing. They are telling the tech that there is a problem upstream, and the tech needs to diagnose the system to locate the fault. To do this they use specialized equipment and manufacturer provided diagnostic trees. That is beyond the scope of a code thrown by an ECM.

There seems to be this belief that cars somehow have sensors on every critical component that can tell when any particular component is malfunctioning in a manner that requires replacing only one part to resolve the issue. That just isn't the case.

What you have is a system that is largely ignorant of what is going on. It has no "big picture." The only thing it knows is sensor J is returning a value not present in the look-up table, therefore we throw a code indicating which sensor value is non-conforming. It is not indicative of a problem with sensor J, Sensor J's input merely triggers the code - that's *why* there's a sensor. A faulty injector, loose gas cap, broken ring land on the piston, exhaust leak, rat-chewed wire, etc. could be the real culprit. There is simply no way for an ECM to know the gas cap simply needs to be removed and replaced in a voodoo fix.

Consider an electric oil pressure gauge. If your gauge reads 2 psi at full throttle, you need to investigate the problem because the gauge cannot tell you how to fix it. The gauge can't tell you if the oil pan is empty. It can't tell you the pan is full but an oil line is spraying oil on the road. All it can say is that the sensor returns a voltage corresponding to 2 psi. You need to look under the hood to know if you have oil in the pan, if oil is spraying out while the engine idles, or if oil only sprays out when you open the throttle. Or if the sender wire connection is covered in corrosion and delivering an attenuated signal.

Many of you seem to think cars are a whole lot smarter than they are.