Your views on CELs please

[spit]

I know that engine management systems are here to stay, and that they are necessary to keep modern cars in tune. But I'm interested to know what you think about the Check Engine Light (CEL) feature?

Reading through the posts here, it seems that the most commonly suggested explanation for a CEL is a sensor fault (like a dirty MAF).

This isn't surprising - the sensors are the most delicate items amongst the fuel/air/engine/exhaust mechanicals. So I'm asking myself, what is the point in having the monitoring system trigger an alarm if it is less reliable than the stuff it is monitoring?

Maybe I'm just too old and want to go back to the days of mechanical points and DIY ignition timing. The cynic in me reckons its a ploy to get us to trundle our roller skates down to MrT's to part with some cash. The old codger element of me says I should go buy a moggie minor and bah humbug to all these new-fangleds.

Don't get me wrong, I luv the '2. I just don't get the logic of this. Most of us can "feel" when our car's performance is a little off. If we look after fluids and servicing needs, then generally everything turns out OK. Now, if CELs warned of impending catastrophic failure, I'd be all in favour, but they just don't. Look at the posts on pre-cat failure - the advice is always the old-fashioned approach - "check the oil level/watch the oil light".

Before you shoot me down, yes, I know the sensors are an integral part of the "necessary" engine management system, so its a bit of a circular argument. But I question whether they're fit for purpose when they are so unreliable compared to the rest of the kit.

What do you all think? Are you with me, or am I mad as a box of frogs for holding this view? Start shootin'!

[Tem]

Personally, I like the lights and trouble codes. I mean the fact that they exist and point to the direction of the fault. Without those you'd be replacing the engine with all accessories every time you have some issues  s:? :? s:?

Then again, I get my living with computers, so they are my 2nd nature anyway...

I wouldn't mind a good old car where the ignition was the most complex electrical system and I actually have one as a 2nd car  s8) s8)  But those things just wouldn't pass current emissions laws for new cars, so it's either the sensors and lights and everything or no new cars at all  s:? :? s:?

[SteveJ]

If you want to kill your engine in pretty short order, please feel free to ignore the "less than reliable" CEL.

Modern engines are run very close to the edge of self anialation (sp?) in order to get the best performance / economy & the lowest environmental impact.

Your claim that you 'know' when the engine isnt performing properly is to put it politely a load of bull - by the time you can feel that there is problem you have probably done some serious damage to the engine.

This is why modern engines are so much more reliable, as (most) problems are fixed before the damage occurs.

If you want to go back to the 'good old days' of 25mpg & < 100bhp from an 1800cc engine, please feel free to transplant a ford pinto into the rear of your '2

If however you want to save yourself a few quid on running to the dealer when the CEL comes on, use the button and go buy yourself one of the PC based OBDII readers.

[spit]

You both raise sensible points guys, and perhaps its my ignorance of mechanicals and computers that needs fixing.   s:oops: :oops: s:oops:  

Like I said, its a bit of a circular argument (although I only realised this in the last paragraphs of my ranting!). Perhaps I should have just asked how people rate the reliability of the sensors in modern cars.

[Tem]

Perhaps I should have just asked how people rate the reliability of the sensors in modern cars.

They could be better, but then again, I suppose they are pretty good for the money. Some industrial sensors that really have to work cost a fortune  s:? :? s:?

[aaronjb]

They could be better, but then again, I suppose they are pretty good for the money. Some industrial sensors that really have to work cost a fortune  s:? :? s:?

Indeed - I was recently involved in a project that involved some medical monitoring equipment (pulse, O2 blood saturation and breathing rate, just to make sure nobody had croaked  s;) s;) ) - each set of three sensors cost £9,000.. (And there were 13 banks of sensors) And those three things are fairly easy to sense reliably..

[Anonymous]

After getting a new fuel tank sending unit put in the wife's car (a Ford Contour), she began to get an intermittant CEL. I took it in for her, and the guys at the garage were puzzled because the code indicated something that clearly wasn't the problem.
As often happens, the oldest mechanic is finally called over for his opinion. He looks at the engine a moment, reaches down and connects a loose vacuum hose onto its fitting. Problem solved.
The "idiot light" nature of the CEL irks me, too, but not as much as the absence of oil pressure and water temp gauges. Gauges are good things, and I like them. A lot.

[GSB]

A CEL only indicates specific symptoms, or specific sensors that have gone faulty. Experience and knowledge are still vital when it comes to using that ino to find the cause of the trouble. No-one trains mechanics properly anymore, so they rely more and more on the computer to tell them whats wrong. Sometimes that info is not enough, or in inexperienced hands, can even be misleading. this is illustrated perfectly in the example above.

If you have a measure of knowledge and experience in these things, and know what the computer is actually looking for to determine what code it flags, The CEL is an invaluable tool. I like it. Modern ECU's with their self diagnostics have saved us all fortunes in fuel. make sure the engine is always properly tuned, starts first time EVERY time, and makes finding faults a doddle. It may look complex, but engine maintenance is no longer the balck art it was in the days of points ignition, carbs and bloody stroboscopic timing guns...