Hello everyone,

I'm experiencing an issue with my brake pedal (basically going to the floor), and I suspect it might be related to the ABS module.

I tried to scan the ABS unit for fault codes using VCDS, but I’m unable to communicate with it: it seems like CAN communication is not available.

Is this normal on a Fabia Mk2 (5J), or should I definitely be able to access the ABS module via CAN?

Any advice or feedback would be greatly appreciated. Thanks!

Edited 14 April14 Apr by StephFR

Have you an aftermarket radio. Quite a few folks on here having trouble reading ecu etc. For some reason the after maaret radios affect can-bus and can stop any communication.

If your pedal is going straight to floor I would suspect a bad master cylinder thats letting fluid past the seals or a major leak somewhere. Is the brake fluid level ok. Check the rear drums if fitted for signs of fluid at bottom as my sons mk1 wheel cylinders were shot and leaking fluid.

Alasdair

Via vcds you have to acces to the abs module, however like said by Alsadir1 it sound mor like a bad master cylinder, have you ever replaced the brake oil? try to disconnect the radio (only if is aftermarket) and see if you gain access to the abs module, in my case with an aftermarket radio I don't have any issue via vcds, but when i've tuned the ecu the revo dealer was having issue, after I've unplugged the radio everything worked.

Did this happen all of a sudden or after replacing a caliper etc. It may be air in the system due to bad master cylinder or when changing something fluid has dropped too low letting air into ABS. If you havent replaced any brake parts or fluid was low I would suspect bad seals on master.

Alasdair

Look also for clutch slave if is leaking it share the same brake fluid

On 15/04/2026 at 18:59, Alasdair1 said:

Did this happen all of a sudden or after replacing a caliper etc. It may be air in the system due to bad master cylinder or when changing something fluid has dropped too low letting air into ABS. If you havent replaced any brake parts or fluid was low I would suspect bad seals on master.

Alasdair

Thank you for your replies.

Sorry, I didn't explain what was already done.

Regarding the pedal brake issue itself, I've already performed a complete inspection (no leaks, no worn-out hoses), bled the system, replaced the master cylinder, and bled it again. The brakes work almost normally, except that if I increase the pedal pressure slightly and hold it for 10 seconds, the pedal eventually sinks to the floor. There are 4 discs.

Regarding the diagnosis, there is no signal on the dashboard, but I'd at least like to check the ABS status/messages. The radio is original (I think it's a 'Car Dance' unit), I'm not sure how to access it. When I check the communication status on the PC, it reads: 'Status Ready / K1 OK / K2 OK / CAN NOT READY'. Does this seem normal to you on this car?

On 15/04/2026 at 19:00, Jack25 said:

Look also for clutch slave if is leaking it share the same brake fluid

I haven't experienced any leak nor fluid level loss. But I'm curious, how/where are they connected?

11 hours ago, StephFR said:

'Status Ready / K1 OK / K2 OK / CAN NOT READY'

The radio is an OEM one so doubt it will be it. I think that message is normally with older cars without CAN. Not sure why as I think yours does unless its an older version or the VCDS needs updated?. I did read that autodetect may not work and you have to choose chassis/engine number manually. I am just learning VCDS so not much help I am afraid but I am sure someone on here will help.

Alasdair

11 hours ago, StephFR said:

I haven't experienced any leak nor fluid level loss. But I'm curious, how/where are they connected?

The brake and the clutch system share the same oil, the clutch does get oil from the reservoir, in the picture you can see the rubber hose, wich is placed around the min level so if there is a oil loss you can stiil brake, but you will not have the clutch hydraulic system.

On 16/04/2026 at 19:56, StephFR said:

Thank you for your replies.

Sorry, I didn't explain what was already done.

Regarding the pedal brake issue itself, I've already performed a complete inspection (no leaks, no worn-out hoses), bled the system, replaced the master cylinder, and bled it again. The brakes work almost normally, except that if I increase the pedal pressure slightly and hold it for 10 seconds, the pedal eventually sinks to the floor. There are 4 discs.

Regarding the diagnosis, there is no signal on the dashboard, but I'd at least like to check the ABS status/messages. The radio is original (I think it's a 'Car Dance' unit), I'm not sure how to access it. When I check the communication status on the PC, it reads: 'Status Ready / K1 OK / K2 OK / CAN NOT READY'. Does this seem normal to you on this car?

Is the engine running when this happens?

With the engine off does the pedal stop at the normal/higher position?

When in motion does the pedal stop at the normal/higher position?

If so it is normal and you never have noticed before.

@Alasdair1 asked the same question a while back, so I thought he would remember.

Can everyone confirm this.

As you changed master it may be a small amount of air in ABS unit that's not coming out. The fact that you get 'Status Ready / K1 OK / K2 OK / CAN NOT READY' may be that there is a bad connection at port or perhaps the port isnt getting power. Check that the drivers for VCDS are up to date and I assume its a genuine cable. I assume you tried with ignition on and engine running. Might be worth checking terminals in port and also lead plus fuses related to OBD port. As far as I know a MK2 should have Can-bus. Can you scan car for codes?

Alasdair

On 17/04/2026 at 08:57, Jack25 said:

The brake and the clutch system share the same oil, the clutch does get oil from the reservoir, in the picture you can see the rubber hose, wich is placed around the min level so if there is a oil loss you can stiil brake, but you will not have the clutch hydraulic system.

Amazing thanks. I didn't pay attention, I thought that drain pipe was an overflow

On 17/04/2026 at 21:36, tetley said:

Is the engine running when this happens?

With the engine off does the pedal stop at the normal/higher position?

When in motion does the pedal stop at the normal/higher position?

If so it is normal and you never have noticed before.

@Alasdair1 asked the same question a while back, so I thought he would remember.

Can everyone confirm this.

The pedal behaves the same whether the engine on or off.
In both cases, the pedal travel looks to be the same at the top and bottom

On 18/04/2026 at 11:09, Alasdair1 said:

As you changed master it may be a small amount of air in ABS unit that's not coming out. The fact that you get 'Status Ready / K1 OK / K2 OK / CAN NOT READY' may be that there is a bad connection at port or perhaps the port isnt getting power. Check that the drivers for VCDS are up to date and I assume its a genuine cable. I assume you tried with ignition on and engine running. Might be worth checking terminals in port and also lead plus fuses related to OBD port. As far as I know a MK2 should have Can-bus. Can you scan car for codes?

Alasdair

Yes I am a bit confused about the way ABS unit works (I'd rather not change it as it is quite expensive).

Maybe there is no CAN on this car as per information on Vcds cable site "The New Beetle continued to use the older k-line diagnostics only incorporating CAN for Generic OBD-2 in 2008 as mandated by the EPA. Other holdover models such as the 7V Seat Alhambra, 6L Seat Ibiza/Cordoba, 6Y/5J Skoda Fabia, 1U Skoda Octavia, 5J Skoda Roomster, 3U Skoda Superb and others may have continued to use the older k-line diagnostics into and past 2008."

Yes I did try off/on/running.

This cable is from a mechanic (working fine on other cars).

Couldn't scan any codes so far but could only get some controller basics informations.

By your suggestions, I guess I could try to remove all fuses and keep only ABS, we never know

Roomster and mk2 Fabia are electronically the same as mk1 Fabia until about February 2010. VCDS lite was/is able to talk to their diagnostics system over k-line.

From March 2010 full VCDS is needed.

However, full VCDS will work with all of the above.

As mentioned though, to do an autoscan you have to select chassis type (5J) manually.

Often, a lack of comms with a module suggests a blown fuse, and ABS has a few.

If you wish, I can tell you which fuses to check (will need VIN, message me with it).

On 22/04/2026 at 04:50, Breezy_Pete said:

Roomster and mk2 Fabia are electronically the same as mk1 Fabia until about February 2010. VCDS lite was/is able to talk to their diagnostics system over k-line.

From March 2010 full VCDS is needed.

However, full VCDS will work with all of the above.

As mentioned though, to do an autoscan you have to select chassis type (5J) manually.

Often, a lack of comms with a module suggests a blown fuse, and ABS has a few.

If you wish, I can tell you which fuses to check (will need VIN, message me with it).

Thanks for confirming that this model does not use CAN protocol, at least, we can rule that out.

Instead of running a full auto-scan, I tried accessing module 03 (ABS) directly.

Sometimes, it appears to see correctly the VAG Number + Component + Soft Coding + Shop (does it exclude fuse issue?)...

but then it keeps switching between different communication protocols (at least that's how it appears).

If I manage to click on "Fault Codes 02" button quickly enough, it eventually returns the message "Too many communication errors to continue".

(It looks like I am not senior enough to send you a message)

Edited 23 April23 Apr by StephFR

I'll message you, you'll be able to reply.

What you're seeing may exclude a fuse issue, but there's no harm in checking them.

By the way, you say

22 minutes ago, StephFR said:

this model does not use CAN protocol

It does, throughout most of the modules.

It's the primary communication system.

Pretty much everything "intelligent" except the window motors use CAN to talk to one another.

But diagnostics is via K-line, even though CAN wiring is present at the diagnostic socket.

Someone with better VCDS knowledge like @PetrolDave may be able to explain that to us.

On 23/04/2026 at 20:58, Breezy_Pete said:

But diagnostics is via K-line, even though CAN wiring is present at the diagnostic socket.

Thanks, I understand better now why it seems confusing… because it is :)

FYI, here is the current situation.

I have checked the ABS-related fuses and they appeared to be fine. However, the VCDS communication issue remains, and the module still returns: 'Too many communication errors to continue'.

Following my fuse manipulation, I am now facing:

• An engine warning with an exhaust system alert

• Loss of cruise control functionality

I’ve re-checked all fuses and fixed one amperage mismatch (not engine-related), but no luck so far. I’m currently driving with the warning light on and I'm worried about potentially damaging the engine or the exhaust system, although I believe my car is not equipped with a DPF. I haven't noticed any change in how the engine is running.

I have tried to unplug the battery for 2 days, but there was no change. Is there another simple reset procedure to try, or specific VCDS settings to stabilize the connection?

I finally found the solution for the engine warning and cruise control issue.

Driving outside the city fixed it. From what I understand, lowering the average fuel consumption helped: I got it down to around 8 L/100 km, and once it dropped below 5 L/100 km the engine warning light disappeared.

After the next restart, the cruise control started working again as well.

The only remaining issue is the VCDS connection problem. If anyone has suggestions, let me know.

On 22/05/2026 at 12:14, StephFR said:

I got it down to around 8 L/100 km, and once it dropped below 5 L/100 km the engine warning light disappeared.

It should read:

"I noticed it was as high as 8 L/100 km, and once it dropped below 5 L/100 km the engine warning light disappeared."

Hi where are you? you need to do proper volt drops on lives and earths at the abs ecu plug (word 03) to rule out verdigris in the loom from the source causing intermittent connections. Once that has been done, scope the comms to see if it is being pulled up/down or has noise. This can be caused by aftermarket sensors/devices/components which would need to be disconnected one at a time unitl function returns. ONCE these have been ruled out, look at getting the abs ecu tested/repaired.

My 5J had a recent ABS issue for the motor (not the same as this issue but!) , I did a volt drop test and although the fuse showed 14.2V at the ecu plug (on Battery Support), when loading the circuit, the voltage at the ecu plug dropped right off.

I will see if I can find a picture.

This shows me initially checking the negative feed to the ecu plug under load of a test light. For larger drop checking I would use a higher load.

The negative of the test light is on the positive battery terminal when testing the first two Terminal 31 pins.

The negative of the test light is moved to the negative battery terminal to test the Terminal 30 and 15 positive pins.

This is a factory breakout box connected to the ABS ECU plug.

Each numbered pin corresponds with the pin on the ecu plug.

The battery has been removed to gain access should I need to open up the loom to find a high contact resistance.

The power is being provided by a 100A VAS battery support unit.

The fault was traced to a fault fuse in the SA fuse box. No output at 10a to the ABS 38 pin1 ABS plug at pin 1 or T38a/1.

I found a high contact resistance between the fuse leg and the terminal in the fuese box. The fuse link was fine.

Confirming repair. NB volt meter also used when checking under load.

Sometimes a much higher load is required, but not in this case.

Edited Sunday at 17:494 days by 3T51704x4

But ........if you have lost your pedal, it will be the hydraulic side that needs addressing first, especially if the master cylinder has been replaced. ELSA says a minimum of 2 bar pressure is needed to bleed the hydraulic system; newer systems require more for the very reason you have experienced. Also, once it has been bled, you need to bleed the ABS with your chosen diagnostic tool in Address 03.