Anyone had any problems with their Octavia starting then cutting out straight away? New battery, alternator & starter motor are fine! All of the lights nearly come on the dashboard! Worked perfect till a few days ago when it rained really heavily! Only been able to start it a couple of times since then & when it does start it drives fine till I go to start it again 👎🏻 Won’t connect to diagnostic machine either 
Thanks 🙏🏼🤞🏼

Sounds like an immobiliser fault. 

I agree with post above if it starts and then cuts out 10 seconds later. This is deliberate when the immobiliser has not received the correct code from the key.  As you have both the immobilier problem and lack of connection to the diagnostic port it could be a result of a blown fuse, poor earth connection or failing battery (usually accompanied by various spurious dash warnings).

 

It would be helpful if you could add more car details such as year of manufacture, model (VRS? Diesel? Petrol? engine size?) or best of all your engine code such as CAYC, BMM etc 

2008,Skoda octavia VRS 2.0 petrol 

Now one of the brake lights won’t go out even when the battery is disconnected 🤔 

the engine management light had gone off now but still having same problem 

The odd few times we’ve had it started it’s fine but then when you try and start again it cuts out like a second later

3 minutes ago, ZoeLM1990 said:

2008,Skoda octavia VRS 2.0 petrol 

Now one of the brake lights won’t go out even when the battery is disconnected 🤔 

the engine management light had gone off now but still having same problem 

Wow free energy!

I assume you mean you disconnected and then reconnected the battery (with a pause of a few minutes) but the brake lights are now on continuously.

Is this what you mean?

Does the diagnostic port now work?

If you only disconnected the battery for just few seconds, do it again as there is storage in the electronics that needs to be discharged.

 

does the cluster power up as it should?

where are located?

Sorry this is coming weeks after your original question, so not really an urgent reply...

You say this happened after hard rain?

It used to be a big issue on lots of VAG cars that he 'comfort module' gets wet and causes problems with lights, immobiliser, windows, etc.
lift the carpet in the passenger footwell and see if there are signs of water under the carpet and soundproofing.

The comfort ecu is in the footwell and gets flooded when water overflows from the scuttle.   Check for leaves/dirt etc in the scuttle and look at the drain holes (under the battery tray in some cars.

if you need to replace the comfort module (CCM) then make sure to get the exactly correct version - there are variants and I dont know if they can be reprogrammed or actually need to be correct.

No ...comfort on octavia mk2 is not there...may u start recording something...because u said your check engine is off maibe engine ecu between wipers is in water, can u check?