I have an X5 E70 4.8 with a disabled CEL (done by a tuning coder).

Can this have be done via coding ? (I.e. can it be re-enabled ?).

or perhaps he just cut a wire on a connector ? (that I can reconnect).

Background :-

A few years back the car was code converted to run Ethanol by an independent specialist. It runs well on Ethanol (E85) but flags up CEL codes for the O2 sensors giving different readings.

I eventually discovered that the guy who did the conversion had disabled the CEL (so it wouldn't be on all the time because of those O2 readings) !

However, correct CEL operation is now needed to pass the regular roadworthy test (MOT, Controle Technique etc.) So I need to re-enable the CEL.

I have a hand scanner to check/reset fault codes, so I know that if I run with a tank of std gaz/petrol before the test, it will be code free for the test.

Sadly I can't ask the convertor guy what he actually did, as he is no longer in business.

Please help !