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sean, Car and LCV technician
Category: UK Car
Satisfied Customers: 3105
Experience:  UK City & Guilds qualified with 30 years experience
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Ford 1.8 ghia: I have a engine warning light come on on my

Customer Question

I have a engine warning light come on on my 52 plate 1.8 focus petrol. engine seems to run fine?
Submitted: 2 years ago.
Category: UK Car
Expert:  sean replied 2 years ago.
Hello, I hope the following assists you.
There are a couple of common causes of the MIL coming on but the engine runs fine on this engine.
An O2 sensor fault either upstream or downstream, the catalyst has failed causing it to become inefficient or the camshaft sensor signal is missing/erratic.
If an O2 sensor fails the engine management compensates for this so the engine still runs OK, the MIL is on as it is an emission problem, the same applies to the catalyst, again the engine runs OK but as it is an emission fault the MIL is illuminated.
The camshaft sensor is used on start up to determine injection sequence but if the signal is missing the engine management will switch the injectors to match the spark so injector 1 and 4 will open together. If this is the case the engine may use more fuel and again this becomes an emission problem.
There are other concerns that can put the MIL on but these usually cause poor running of the engine.
The only 100% way to pinpoint the sensor or actuator causing the problem is to carry out a diagnostic scan on the engine management and retrieve any stored fault codes. If you want to do this on a DIY basis there are many code readers available on the internet and there are now mobile phone Apps.
If a garage is doing this then the cost should be minimal as all garages are equipped to read engine management codes.
I hope this helps but if I can provide further information let me know and I'll reply as soon as I'm able to.
Best wishes,