Hi guys! Hopefully someone can shed some light on some odd issues with my skoda fabia i just bought.

its a 2006 1.9 tdi (100bhp) elegance model i think.

 

basically when my cars off the indicators and hazards work perfect, and when i first start the car the same, but as soon as i add some revs or start driving, the whole right hand side stop working? No ticking nothing, but if you switch it off and back on they work again.  When there not working if you press the hazards switch, the indicator bulbs all work but no indicator.

 

also if its related, sometimes the traction control light will randomly light up, and when it does if i plug in a code reader i says it can't establish connection, but again, if you turn the car off and or back on so the light dissapears the code reader works again but cant find any faults...

 

would i be right in assuming its a bcm failure?  Im pretty sure the mpg calculator doesnt remember any reading either as its always oddly low.

 

many many thanks in advance if anyone has any ideas.

 

p.s ive checked fuses and stuff and changed one sidelight indicator that was blown (thought that was the problem...no joy)

Check battery voltage (across battery posts) before and after starting engine (and when revved). Charging faults and poor connections can cause all sorts of weird behaviour.

 

The indicators are driven by an integrated circuit in the BCM/Onboard Supply Control Unit. I guess it will have overload protection, so  may behave differently at different system voltages (e.g. as revs change on a system with poor regulation).

Not sure what causes the TC light to misbehave, but again, rule out voltage issues first

The mpg calculation I would expect is done within the instruments/clocks panel but could be in BCM. Seems unlikely to be related, to me.

Edited 10 August, 20187 yr by Wino

Thanks for the reply wino, il certainly test out the voltages when on and off, if its voltage spikes, what most likely to be the cause? Any idea?

6 minutes ago, Dangetto said:

if its voltage spikes, what most likely to be the cause

Alternator voltage regulator, I imagine.

1 hour ago, Dangetto said:

When there not working if you press the hazards switch, the indicator bulbs all work but no indicator.

I guess you mean no ticking or telltales lighting in the cluster? Strange.

Correct, not even the arrow indicator, just doesnt do anything when you indicate right...then odd part is hazards work all round the car, yozu can literally indicate right, leave the stalk up(right) and nothing, press hazards, all bulbs flash, unpress they all stop.  Left side work fine no matter what you do. Il try checking voltages etc tomorrow and see how they seem.  I debated trying a load resistor on all the right hand indicator bulbs just incase the voltage is spiking and causing the failure.  Sorta like what happens if you fit aftermarket hids, il try all the checks first see what they uncover. Thanks so much for the help so far though

I'll have a look at the wiring diagrams if I get a chance, bit of a complicated one for a Friday evening though!

I guess when all six bulbs are called for by the hazard light switch the 'pull down' of the system voltage is twice as much each time the filaments are powered, so any excess voltage/current will be less than when just one side is requested. Can't imagine the reason for the cluster to not be aware of what's happening though. 

Thats super kind wino thanks very much buddy, its a wierd one!  Closest thing i could find was bcm failure as its just the one side, from google i found someone had similar issues and it was his bcm, im hoping not as its coded to the car and i imagine fairly expensive. So im gonna try the cheaper routes first.

the other chaps issues was voltage spikes causing a part of the bcm to shut down hence why i thought about trying load resistors to trick you the bcm into thinking its a set voltage, again though of the bulb upgrades and how they throw issues due to low voltage. I know mines likely the other way round, but the resistors should make the bcm think its running correctly. Clutching straws i know, but I certainly check the battery and alternator for spikes when i put it under strain etc as per your recommendation cheers dude

Secondhand BCM could be only a few tens of pounds, and if from an exactly-same equipped car, coding would be right already I think; if not readily changed with VCDS.

 

After your battery/charging voltage checks, if you still have a bit of enthusiasm, you could access the BCM by dropping the lower dash panel (various how-to  descriptions for this in 'Fabia Guides' section like this one https://www.briskoda.net/forums/topic/61180-fabia-evap-temp-sensor-how-to-with-pics/). You could then read all the part number info off it and maybe do a quick resistance check on the left and right output cables to the indicators.

There'll be a black 16-way connector plugged into a position labelled XS6, if you unplug that then measure resistance from pin 14 (black/green wire), and pin 16 (black/white wire) to chassis, you'll be measuring the resistance of all 3 bulbs in parallel on the right and left sides of the car respectively.  Do all this with ignition off, key out.

 

Make sure you have the right bulb types both sides, front and rear, PY21W, with the pins on the sides offset at 150 degrees, not opposite each other. You can just about jam the standard PY21 type in, and a previous owner may have done this unknowingly.

 

Awesome! You my friend are a genius ha, il have a good look about as soon as im able and il post back here if i get anywhere. Thanks so much for your time and extreme knowledge! Much appreciated!!

8 hours ago, Wino said:

You can just about jam the standard PY21 type in, and a previous owner may have done this unknowingly.

 

 

I found that someone had done that to one of my rear ones when I first got the car.

Bcm  looks fine no dry solders, cracks, nothing. Im waiting on a better mutimeter to see if i can trave any spikes, and i bought new bulbs all round so will see if that fixes the issue.  

So lets say the voltages are fine and new bulbs dont help, that would point at bcm right?

im wondering if its possible to cut the wires the pin 14 n 16 and adding a flasher unit and live circuit to a empty ignition live fuse, would this work? So essentially adding in a separate flasher relay etc like older cars

I think you're looking for a charging voltage that's consistently excessive, rather than spikes, for what its worth; so any old meter will tell you that.

So guys bit of a update, after unplugging the bcm i found no faults, multimeter on battery car on and off was fine. But after plugging it all back in it seems the indicator issue has resolved itself! Yay!...but...now the front wipers seem to be on permanently until i indicate, you guessed it, right lol then they stop. And i have an airbag light on too haha. So im defo assuming it bcm board. For now, im going to wire a 'old school' off n on switch to the wipers as a temporary measure so i can at least drive it about.

any final ideas or would you agree its bcm? Cheers guys

Not sure that the airbag system has much to do with the BCM, but the wipers are definitely controlled by a couple of relays within it.

 

7 minutes ago, Dangetto said:

multimeter on battery car on and off was fine

What were the voltages?

 

How dry is the car internally? Any door carrier leaks and wet carpets? Any sign of any moisture or corrosion on any of the BCM connections?

Its was just over 12 when the car was off and 13.4 running, and when revs were raised around 3-4k the voltage was around 14.1 where the indicator would cut out.  No damp anywhere, the connections look perfect, literally no idea. It even wierder that moving connection about seems to have resolved one problem but created another.  All connections seem secure too, perhaps somewhere in all the wiring its loose or theres a tiny break, either that or its gotta be the bcm itself, didnt look like it had been tampered with or damaged in any way, least the indicators are working again, and il have a kit car esk set of wipers if i put them on a switch until i can get another bcm.  Im just hoping no other issues arise over the next few days, il try my code reader on the airbag light though im betting it wont show, il keep updating with anything i find! Thanks agin for all the help

How old is the battery? Those first two numbers are low, especially the 13.4.  Even the 14.1 is a little low unless the engine was hot, and some electrical loads were switched on at the time.

Can you (safely) get your meter probes onto the output post of the alternator and the body of the alternator (on a patch of scraped clean metal) to check that it is putting out the expected 14.5V, with engine cold, just started up. Measuring locally can help to confirm that the alternator itself is OK.

 

 

Irrespective of charging system shortcomings, I can't help thinking this is a wiring loom somewhere rubbing on something metal, possibly near the steering column. Various wires are grounding, giving the BCM unreliable input information???

Honestly i have no idea of the battery age the cars a very recent purchase, i though they were a bit low but assumed it was alright as the car always starts instantly, il certanly try measuring the alternator and see what numbers that shows, im guessing if there low it means the alternator regulators had it?

i hope its not wiring loom hahaha theres alot of it, but il see about taking off the steering cowl n see if i can see anything,. Cheers very much wino! So far despite the cars unfortunate issues, this forum has been the best ive been on in regards to welcomes and especially your help! Much appreciated!