Whilst diagnosing some problems on my new to me 01 TDI, I've realised the CEL does not come on when the ignition is turned on. Is it possible and has this been turned off via VCDS...and if so can anyone tell me how to switch it back on again. I'm pretty new to VCDS. Also what reason would someone have to switch it off??

One would imagine the only reasons were disabling it were:

- car was knackered and about to blow up

- car has been modded and one of the sensors keeps throwing up a fault code

That said there are not many diesel mods to do which cause that, assuming your car still has most of the factory fit bits under the bonnet.

I am not sure that my light comes on when I turn the ignition... i'll go and check in a bit (2001 Elegance TDI)

One would imagine the only reasons were disabling it were:

- car was knackered and about to blow up

- car has been modded and one of the sensors keeps throwing up a fault code

That said there are not many diesel mods to do which cause that, assuming your car still has most of the factory fit bits under the bonnet.

I am not sure that my light comes on when I turn the ignition... i'll go and check in a bit (2001 Elegance TDI)

It's bog standard under the bonnet, when I got it the only problems I found were leaking turbo seals and a leaky EGR. Also some bright spark had removed the engine breather hose, probably trying to reduce the amount of oil in the intake system without realising it was coming from the turbo. Wonder if that would've triggered the CEL so they switched it off.

Edited 20 December, 201114 yr by YHNW

cant be turned off afaik. Sounds more like the above and its either been covered with some tape after taking the clock unit out or the LED has blown.

It's bog standard under the bonnet, when I got it the only problems I found were leaking turbo seals and a leaky EGR. Also some bright spark had removed the engine breather hose, probably trying to reduce the amount of oil in the intake system without realising it was coming from the turbo. Wonder if that would've triggered the CEL so they switched it off.

I have re-routed my crank case breather pipework - it only went into the cold air intake after the MAF (as standard design), and blocked off the EGR too :-)

Problem is the breather pipe was removed but it wasn't routed elsewhere, it was just missing. The intake was sucking in unfiltered air downstream of the MAF. Very clever!

Edited 20 December, 201114 yr by YHNW

Problem is the breather pipe was removed but it wasn't routed elsewhere, it was just missing. The intake was sucking in unfiltered air downstream of the MAF. Very clever!

That is never going to help...... unmetered and unfiltered air going in :-(

do all octavias have a CEL?

i've never seen mine come on even when scanning for faults. its a throttle cabled petrol with the older style rectangle cluster, the manual isn't too helpful.

cheers,

toby

One would imagine the only reasons were disabling it were:

- car was knackered and about to blow up

- car has been modded and one of the sensors keeps throwing up a fault code

That said there are not many diesel mods to do which cause that, assuming your car still has most of the factory fit bits under the bonnet.

I am not sure that my light comes on when I turn the ignition... i'll go and check in a bit (2001 Elegance TDI)

Dear mbames,

I have learn a lot from reading your posts about sticky vanes VNT thank you! .... and investigation is next on my list of faults with a 2001 Elegance TdI that i have viewed today.

However before i proceed further can you confirm the CEL illuminates upon first turn of the key please ?

Thanks in advance,

SuRiV

Edited 15 March, 201214 yr by SuRiV

engine light should be on with ignition and go out when engine running. mine doesn't work either

Hmmmm. So best advise is that i need to use a VAG COM to be sure of any stored ecu faults

From the other post i started today, it appears that some CEL don't work and some models don't have a CEL : confused: