I fitted a tow bar to my Superb last weekend before I started I already one warning light for a front fog lamp bulb. The trailer lights were working as they should so I assumed everything was okay. On replacing the front fog lamp bulb that error light went out. But when I put the dipped lights on I found the bulb warning light came back on, when scrolling the wheel on the steering wheel found I had two warning messages for either rear tail light.  I've disconnected all the tow bar wiring except for the indicators. The warning lights still remain on? How do I cancel them? I've used VCDS but that's not coming up with any errors or error codes?

It's not a matter of cancelling. Have you merged the side light wiring onto one feed for the trailer socket somehow?  - this would confuse the individual bulb detection. If you can undue all the wiring changes to see if all ok - the lights are re-tested when you turn the ignition on. Can I presume you haven't changed anything else such as car rear sidelight bulb type etc?

Did you use a bypass relay module as part of the wiring?

Edited 18 December, 20214 yr by bigjohn

Yes I've used the bypass relay that came with the tow bar. I haven't changed any of the bulbs and all 6 side light bulbs are working on the car. Two of which are a combined brake & side light bulb.

 

The brake, side lights and indicators were all working as they should on the trailer board. I don't know about the fog light as my trailer board hasn't got one. Though I think I may have scotch locked into the wrong wire for the fog light? Connecting to the  feed instead of the common as I didn't fully understand the wiring instructions.

 

I've now disconnected the reverse light, brake light and fog light feeds to the trailer bypass relay. I've left the indicator feeds to the bypass relay.  I didn't connect either side light feed to the bypass relay as per the relay instructions. But the bulb warning still comes on for both rear lights. I guess I should now also disconnect the indicator feeds to the bypass relay and see if the warning goes off? After that the only thing I can think off is disconnecting the battery and see if that turns the warning off.

 

The wiring colours change at the plug where the lights connect to the main loom. The two black wires you can see in the photo merge into one at the plug and join into 3 earth wires which are all joined at one point and split back into 3.

 

Edited 18 December, 20214 yr by Derbyshirebod
Rotate the photo

I have also found that Bulb Warning can come on just before the bulbs blow

Might be a wise time to change all bulbs just to make sure 

They cost buttons

On 18/12/2021 at 22:48, Derbyshirebod said:

I haven't changed any of the bulbs and all 6 side light bulbs are working on the car. Two of which are a combined brake & side light bulb.

 

There are 8 not 6 rear side / night lights on the estate (and Twindoor).

 

In your picture, the fog light bulb (in the same way as the brake light bulb) is dual-function, brake / tail and fog / tail, this makes-up the lower portion of Skoda's signature 'C' shape of their rear lights.

 

The brake / tail is W16W, the fog / tail is P21W, both single filament, the output is varied via a single filament by the BCM / CECM.

 

Are all 8 tail light bulbs functioning correctly?

 

Edited 21 December, 20214 yr by silver1011

On 19/12/2021 at 18:52, DEL80Y said:

I have also found that Bulb Warning can come on just before the bulbs blow

Might be a wise time to change all bulbs just to make sure 

They cost buttons

Thank you!  Good call changing the bulbs has resolved the problem, Though at £9.60 for 6 bulbs from my local motor factors I thought that was a bit steep? Though they probably would have been cheaper had I bought them online. So none of the 6 I changed had blown, though yes there are two bulbs with broken filaments in the photo because I dropped them in the motor factor car park. So after changing the bulbs and turning the lights on the bulb warning light was still on! Tough then checking the warning message it was now saying check the rear number plate light bulbs!  Turning the ignition off and on the warning light went out and hasn't come back on. Checking the rear number plate bulbs they are quite black so I'd better change them as well'

8 hours ago, silver1011 said:

 

There are 8 not 6 rear side / night lights on the estate (and Twindoor).

 

In your picture, the fog light bulb (in the same way as the brake light bulb) is dual-function, brake / tail and fog / tail, this makes-up the lower portion of Skoda's signature 'C' shape of their rear lights.

 

The brake / tail is W16W, the fog / tail is P21W, both single filament, the output is varied via a single filament by the BCM / CECM.

 

Are all 8 tail light bulbs functioning correctly?

 

On checking you are indeed correct! 8 and not 6 as I'd thougth. I had not checked very well and didn't realise that the rear fog light bulbs were also dual function.

All 8 bulbs were working correctly. Though I only change the 6 bulbs I mentioned in my last post, which has turned the warning light off. I've also disconnected all the tow-bar wiring, which I now need to re-connect, which I had connected correctly.

Result! 👍

5 hours ago, silver1011 said:

Result! 👍

Yes indeed!😊  

Though I could have saved myself a load of grief had I changed the tail light bulbs in the 1st place! Instead of assuming I'd made a mistake with the tow bar wiring and stripped the boot lining out for a 2nd time and disconnected all the connections I made.

The OE tail-light wiring is dreadfull, really shonky, until the later photograph which I enlarged I thought you had done a bodge job with the trailer wiring.

 

Their wiring is thin and brittle as it is without having long unwrapped unsupported lengths of it like that; the green conductor already looks like it is fracturing.

16 minutes ago, J.R. said:

The OE tail-light wiring is dreadfull, really shonky, until the later photograph which I enlarged I thought you had done a bodge job with the trailer wiring.

 

Their wiring is thin and brittle as it is without having long unwrapped unsupported lengths of it like that; the green conductor already looks like it is fracturing.

I didn't make any connections to the light assembly harnesses as you say those wires look some what on the delicate side.

I used the scotch locks which came with the tow bar and made my connections to the main loom inside the car on the passenger side to the heavier wires. The tow bar wiring was relatively straight forward once I'd identified which wires to connect to. I had to take an extension wire from the drivers side of the car from the OS indicator. Instead of running a +12V wire from the cars fuse box / battery to the bypass relay as suggested in the fitting instructions I scotch locked into the +12V feed to the auxiliary socket in the boot.

 

I suppose the new tow bar wiring connections to the side light circuit must have affected the balance of the load and caused the dash board warning light to be activated ?

I wired mine in the same way from the auxiliary socket.

 

The bypass relays only take a miniscule trigger current so should not produce any bulb warnings, I have fitted them to my last 2 vehicles (Octavia 2 and Yeti), they are far superior to the old school ones especially in regard to the audible warning for the indicators, no more mucking around tweaking inductive current sensing coils.

 

I detest Scothlok connectors but there really isn't any better alternative, I use BT type glycerine filled ones that are better sealed and dont cut into the wire quite so much.

 

The rear light cluster in both vehicles was one piece with metal busbars running to the individual bulbholders, the insulated loom ran to the connector which had strain relief for each conductor in one piece, what it fitted to your vehicle looks like the cheapest of Toytown aftermarket styling accesories, I am shocked that VAG whose wiring even back in the days of the Beetle was streets ahead of any other manufacturer should have stooped so low.

 

I am still a Skoda fanboy but won't be buying a vehicle any newer, if this one continues to be as troublesome as it has, not bad but nowhere near as good as the previous ones then it will go and I will buy the best looked after oldest model I can find, somewhere between 2001 and 2006 is the sweet spot for me.

On 23/12/2021 at 22:54, J.R. said:

I wired mine in the same way from the auxiliary socket.

 

The bypass relays only take a miniscule trigger current so should not produce any bulb warnings, I have fitted them to my last 2 vehicles (Octavia 2 and Yeti), they are far superior to the old school ones especially in regard to the audible warning for the indicators, no more mucking around tweaking inductive current sensing coils.

 

I detest Scothlok connectors but there really isn't any better alternative, I use BT type glycerine filled ones that are better sealed and dont cut into the wire quite so much.

 

The rear light cluster in both vehicles was one piece with metal busbars running to the individual bulbholders, the insulated loom ran to the connector which had strain relief for each conductor in one piece, what it fitted to your vehicle looks like the cheapest of Toytown aftermarket styling accesories, I am shocked that VAG whose wiring even back in the days of the Beetle was streets ahead of any other manufacturer should have stooped so low.

 

I am still a Skoda fanboy but won't be buying a vehicle any newer, if this one continues to be as troublesome as it has, not bad but nowhere near as good as the previous ones then it will go and I will buy the best looked after oldest model I can find, somewhere between 2001 and 2006 is the sweet spot for me.

Yes these new bypass relays are a far superior way of connecting the tow bar wiring to the car. This the 1st time I've used one, the trailer bulbs are brighter and don't dim when more than one function is being used. 

I've checked and I don't think any of the light unit harness wiring insulation is brittle or cracking 🤔 

My socket did not work when I towed my UK neighbours trailer, it was OK on my tester here in France, tonight I coupled a roulotte to shift some stuff tomorrow, while I was attending to a dodgy indicator bulb the relay failed in front of me, it had had the lights and hazards going for about 20 minutes.

 

I think it might be the power to the relay from the accessory socket, it has a switch & fuse & the voltage is dropping to 7v, a daylight job.

 

Just as well it has failed now as I have some 10 hour fully loaded and then some! trailer journeys to do soon.

 

I hope its not the relay because we need to have confidence in these things, I would rather it was my own shortcoming.

47 minutes ago, J.R. said:

I hope its not the relay because we need to have confidence in these things, I would rather it was my own shortcoming.

Maybe a dodgy scotch lock connection ?

I use very good glycerine filled Molex BT splice connectors, far better than Scotchloks and have not had a bad connection yet.

 

Probably a crimp spade terminal to the switch or fuseholder, both require the side panel taking off which is a real pain as I have a variofloor with tons of junk beneath it, hopefully I can release the top rear edge.

 

 

Side panel on you Yeti?  it's a PITA taking the side panel off on the Superb as well ! You cant lift the panel without taking loads of other trim of 1st 😞

 

These things are sent down to try me!

 

It will be a screw up of mine and not failure of the module, thats what I am hoping anyway.