Creating a problem

[AndrewSchofield]

Is it possible to, very quickly and with no tools, tamper with something under the bonnet which would cause the engine warning light to come on?

Im selling my car- a '52 plate petrol fiesta. Had someone look at it last night and he brought 'a mechanic' with him to check it over. He looked under the bonnet for a minute or so, then when I started the car, the engine warning light was on. The car has been stood since mid-November, but the light wasnt on before then. Ive started the engine a few times since mid-Dec and no warning lights were on. This Monday night I started the car and drove it from the rear of my house around to the front ready for him to come and look at it yesterday, again, no warning light. Seems very odd that after his engine compartment inspection there's suddenly a warning light on. Is it possible he could have done something, maybe even inadvertently, thats caused the warning light? I didn't see him do anything other than look, and the only tool he had was a torch. That said, I cant say I was watching him like a hawk....

He hasn't mentioned knocking the price down due to this fault, but I'm expecting it to come.....

 

[Burnerman]

Disconnecting one of the various sensors around the engine could certainly cause this - but more likely than not, the engine or general performance of the car would be suffering.
Look for any disconnected wires or small rubber pipes!
Of course, as the management lamp is on, a fault code will be stored in the cars on board computer which can be read (and cancelled) by anyone with suitable diagnostic equipment.
John

 

[AndrewSchofield]

Thanks John, ill have a look tonight. I did wonder if something could have been quickly disconnected and raise this fault. The guys seemed genuine enough, but it just seems an odd coincidence.

Took the car out for a test drive after this happened-light stayed on but I didnt notice the engine running any different to normal or any lack of performance. Would I be right in thinking a diagnostic test is gonna cost around £20?

 

[Burnerman]

It varies, but that price has to be from an independant garage, I think!
If there's no performance difference, expect that to be a lambda sensor issue in the exhaust....there's a chance the lamp may go out by itself, after a run.
John