How smart are ECUs?

Having recently got my first car with an ECU (my previous was a Carlton - no ECU - that served well for 16 years) I was wondering just how smart the modern ECUs are. Will they detect virtually any problem with an engine and if it is not running at peak performance/efficiency?

Any comments to educate me (on this subject anyway) would be appreciated.

Vin.

appreciated.

It seems they adjust the settings to the way you drive and the road conditions. My diesel Astra on tick over run about 850 rpm in neutral, put it in first and it goes up to 1000rpm which can take some getting used to. Supposed to avoid you stalling in traffic jams. Also having travelled on motorway the ECU adjusts itself to morway driving, which means when you leave the motorway th acceleration is a little sluggish until it re-adjusts.

As for problem detecting, luckily I haven't had any yet.

Be aware some ecu's generate more problems than they avoid, although they are designed to detect problems. For instance airbag errors on Rover models can be a bit of a pain, sometimes requiring you just to go the dealer and lost an amount of money to have it "reset". Depends on the car make and the level of luxury/features, usually (eg abs, air conn) as to what diagnosis systems it has. These things can be a source of additional cost later so you may consider opting for a more basic feature vehicle that is easier to repair unless you aren't bothered about forking out for this kind of maintenance on a more luxury vehicle.

I havent heard of any cars that indicate a particular level of innefficiency though aside from the usual petrol consumption gauges etc. Most ecu's are driven for the sake of the feedback to the engine not the driver - if they go wrong you might only know about it because the car is unresponsive, although its possible a service light might spark or something?

Tony

The Rover SRS system can be reset by the home user without special tools.

It varies - but ECUs are used, directly or otherwise, to keep exhaust emissions down. This is why the engine can do strange things from time to time, such as when you lift off, it continues to run for a moment until reverting into "overrun" mode.

Most will compensate for some problems, but not all. If you run out of coolant it'll still die, but if you have an air leak, it'll run, and probably log that it's compensating for something.

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"I'm going to give you a short course in reprogramming with an axe"!