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Hi, As anyone upgraded ABS model on Octavia MK2 1.8tSI

Provided the BCM is correctly adapted to the replacement battery type, there will be no problem replacing a EFB with AGM.

Hi Friends, Can you help me in swapping the BCM on a Škoda Octavia MK2 to enable more functionality.

@MikeT850 was the problem fixed FOC - or did you reject?

As above, red indicator on fob should light when button pressed, regardless of vehicle status. Are you sure replacement cells were inserted correctly - and any protective sticker on cell was fully removed before use?

If the high beam is activated, pulling on the stalk (like you would pull on it to manually flash, not toggle) should deactivate it (so disabling manual toggle or automatic highbeam).

Red light on fob should light up. Does on my sons MK1. If theres no light maybe as said new batteries may be at fault. Seems very unlucky for two fobs to fail at one time. Alasdair

The "small battery" will be the back-up battery for the Fabia's emergency SOS eCall system and was discussed here in February 2026. https://www.briskoda.net/forums/topic/538090-backup-battery-trouble-code-b1916f4/ Online comments suggest an average reliable working life of 3 to 5 years and, although a new battery may be (fairly) inexpensive, to actually replace it can be a very labour intensive task as there's no standard place in cars for the battery to be located. At least from your comment, it sounds like the eCall battery in Fabia Mk4 models is reasonably accessible.

Hi Pab Would you be able to send me the link ? many thanks Mick

More worried about damaging it with mapping 🫣😂

No worries. I think golf etc is in the bumper too

No. Replaced both fob batteries. No change. Q: Would you expect to see the red LED light with key presses on the keys, even if something amiss at the vehicle end?

Try an other battery for fob. I have had a couple that even though they were new battery they were pretty old and past it. If that doesnt work reckon an autolocksmith. Could be the car battery has gone flat even though it was working the day before. (interior light on etc) Had this problem a few years ago. Old car that hardly got used and car battery went flat with doors locked. Same problem manual entry was seized as was never used. We got a couple of jump leads and put power to main starter motor terminal and an earth to chassis to jump the car with 12v and managed to unlock it. You could also see if you can get to the bonnet release through or near front grill. Alasdair

not the best, it is old version till 2018. but it will survive..

Welcome to the forum. Have you managed to unlock the vehicle after replacing the fob battery?

In the previous update I completely failed to mention the one thing I found which almost certainly contributed to the reliability issues. Doh! Near to the ECU plug in the engine loom, the insulation of the N75 valve signal wire had a significant hole in it. There was sufficient surplus length in this wire to allow me to cut out the damaged section and solder the cut ends either side. I did not find any corresponding damage in the injector wires, but I did replace the ECU plug at the end of this loom with a new OEM one. Getting rid of the carbon cannister produced a couple of collateral benefits, in addition to removing a potential root cause of poor reliability in the wiring. The first of these was a minor simplification of the under-bonnet plumbing. The cannister purge valve releases vapour from the cannister into either the turbo inlet pipe (TIP) or the inlet manifold, depending on pressure differentials. As the carbon cannister was located at the NSR of the engine compartment and the connection to the inlet manifold is on the throttle body at the OSF corner, this meant there was a hose running all the way along the back and off side of the engine, plus a branch from a T-piece into the TIP. This is now gone, and the inlet manifold and TIP have blanks fitted instead. This is only a small win, but it is one step towards the planned overhaul of all of the engine hoses. One length of this hose is currently employed along the top of the NS inner wing, between the fuel tank breather pipe and the rollover valve by the back of the headlight. Another win, small again, is that the ECU mounting bracket incorporated a bracket to mount the carbon cannister. With this no longer being required, I trimmed the ECU bracket to remove both the carbon cannister bracket and another bit designed to support the clutch cable (I think). My Caddy has a hydraulic clutch so that support is of no use. Having tickled the ECU bracket with the angle grinder, I gave it a quick go of the satin black paint. The photo shows the trimmed and painted ECU bracket, with the surplus carbon cannister attachment alongside. The final collateral benefit is the freed-up space. This makes it much easier to access the wiring in this area, and will facilitate some further relocation / tidying in the future. I swiftly found a new use for the vehicle-side loom ECU connector which I had removed a few days ago. Previously I tried and failed to make a cable to enable me to do a VCDS scan of an ECU on the bench rather than in the car. Investigating the current unreliability has led to me increasing my knowledge of the wiring around the ECU, and this included the diagnostic connections. Applying this knowledge allowed me to get right what I had previously got wrong, and have my new comms cable work first time.

Thank you all for help. I've purchased: - Varta EFB N70 Battery - Bosch C30 Charger to try recover old battery & potentially charge the new one - Vgate iCar Pro 2S to code the new battery - intAct Battery-Guard Monitor Now just praying things will arrive, especially worried about battery.

Hi, Correct me if I'm wrong, but I fear EFB and AGM are note fully interchangeable. IMHO If OEM battery is EFB, I'd rather go for an EFB instead of gambling a bit on AGM.

Sounds like you've dealt with it sensibly. A cut or tired valve core seal can cause a slow leak, so it's worth rechecking that tyre's pressure after a few days to make sure it's holding. Also make sure each valve has its cap on, as the cap helps keep dirt and moisture out of the valve.

Good shout, Binx. A monitor like that is handy for spotting a drain, since you can watch the voltage dip overnight. Konrad, if the new battery also sags after a couple of days parked, that would point to something staying awake, so it's worth keeping an eye on the readings once you're sorted.

Yes, I saw everything, I had the Kodiaq and Octavia in mind. Sorry for the incorrect information.

Radar is behind panel in centre of top grille.

2017 Mk3 Saloon 1.2 110 SE-L. Came out to vehicle earlier today - neither key working (no red LED when unlock pressed), and zero response from vehicle. Confident 12v battery is decently charged (successfully used day prior...) Changed key coin batteries (BUT - both keys flat at same time?) Went for manual key entry, so removed drivers door handle cover. The key inserts, BUT barrel rotates freely 360 degrees - no unlocking! Therefore - UNABLE to enter vehicle, and needed to bus to work. Any ideas, please? :-(

Oh man, doesn't it have the radar in the bumper? Sorry, I had that wrong in my head just now 😞

MQ 250 seems to be my transmission code Got it from my build sheet That better?