Help - X5 E70 CEL disabled - need to re-enable.

Grooveworks · #1 10-10-2025, 07:56 AM

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 !

andrewwynn · #2 10-10-2025, 08:58 AM

Does the MIL light when you first turn the key on before you start?

also, the scanner should show you if the indicator light is on.

If no light at pre start then likely it's a cut wire or bulb pulled out.

–awr–

Using Tapatalk VIP on iPhone

Grooveworks · #3 10-10-2025, 09:12 AM

Thanks for the reply Andrew - but no, with the key in, before starting, all other symbols light up but the CEL is always off. Even when there is a fault that should light it !

andrewwynn · #4 10-10-2025, 10:39 PM

Then it's likely a cut trace or missing/disconnected lamp.

–awr–

Using Tapatalk VIP on iPhone

Grooveworks · #5 10-11-2025, 06:54 AM

Thanks Andrew, looks like I need to pull out the instrument cluster and check if he's done something like that.

andrewwynn · #6 10-11-2025, 08:33 AM

That's what i would do. You might have a hint with what error message is stored. Likely a cluster error like airbag light fault. I recently fixed a similar error on an f150 when the passenger airbag light was burned out. When the DME can't read the Ω of the lamp it sets an error. I would expect similar error for missing lamp for MIL

–awr–

Using Tapatalk VIP on iPhone

Grooveworks · #7 10-11-2025, 09:46 AM

The problem is, the MIL/CEL lamp does not light ever (all others lamps are OK). It should be on initially with the ignition on (but not started) even if no faults exist.

I was mainly concerned (and wanted to know if it's possible) that the guy who did the tuning for Ethanol had disabled the lamp in the coding. But having now found out how easy it is to lift the instrument cluster I need to check if he's done something physically with this first.

Grooveworks · #8 10-31-2025, 10:29 AM

I took the instrument cluster out, and the label seal had been cut, so someone had definitely been in there. Got it on the bench, opened it up, and sure enough there was a piece of black tape covering the MIL/CEL lamp !

Removed this, and the lamp now works fine - it's on before starting, and (once I'd cleared all the codes) goes out when started.

Thanks for your help Andrew

andrewwynn · #9 10-31-2025, 11:39 AM

Whew! I'm so glad it was tape! Removed SMD resistor would have been so much harder to fix!

–awr–

Using Tapatalk VIP on iPhone

Grooveworks · #10 10-31-2025, 12:06 PM

Yes I was pleased about the tape. I'm an electronics engineer so re-soldering components/tracks wouldn't have been too much trouble for me, but I was still glad it was just a bit of tape to remove. I was more worried that it had been hard coded off, as I don't have coding tools or access to anyone that has.

I just have the valve cover seals to do now (leak when cold) which I'm not looking forward to ! - but I've already done the oil thermostat/alternator brkt seal - which is supposed to be the worst job. It was indeed a real pita, working blind with one hand, with almost no room to get tools on the various bolts, and only able to turn them a quarter turn at a time.