Multiple dashboard warning lights. No communication with ABS Module

[VAskodas]

Hi y’all. 
Im new here so bear with me. 
So straight to the point. My issue is, while driving in rainy conditions suddenly many faults appeared on dashboard and my speed gauge dropped to zero. The faults are: ABS, AFS cornering lights, AIR BAG, tyre pressure monitoring, Steering angle sensor, Parking assistant and some others. After a while all faults went away. While driving once more the faults appeared all together but I didn’t stop the vehicle. After a full scan with the OBD ELEVEN i noticed that the ABS has no communication and I couldn’t even see the module. Any ideas???

[ApertureS]

First thing will always be check for:

power at the module plug

a good ground that is load tested not just resistance check

then look for your voltages on the canbus wires

 

If all of this tests okay, then you are looking at a failed ABS module.

[VAskodas]

1 hour ago, ApertureS said:

First thing will always be check for:

power at the module plug

a good ground that is load tested not just resistance check

then look for your voltages on the canbus wires

 

If all of this tests okay, then you are looking at a failed ABS module.

Power and module plug are ok. The can bus wires is the way to go I believe. I’ve researched the communication can bus errors and came up with some useful info as you described above, that is to check the canbus wires for open circuit, short to growing, voltages and resistance. Thanks for  your reply. Any further input will be appreciated as well. 

[ApertureS]

9 hours ago, VAskodas said:

Power and module plug are ok. The can bus wires is the way to go I believe. I’ve researched the communication can bus errors and came up with some useful info as you described above, that is to check the canbus wires for open circuit, short to growing, voltages and resistance. Thanks for  your reply. Any further input will be appreciated as well. 

Saying power and plug are okay doesn’t help much, what actual checks were done for the power supply and what was the outcome of this test.

 

as In, what pins were checked using what tool and what was the output reading in what state was the car.

 

was the ground load tested and on what pins?

 

Regarding the canbus - you’re looking into that too much without doing the basics and the above checks first. If there was a short to ground or to the other can wire you’d have no comms with a lot of other modules or it would be running in 1 wire mode. For the canbus all you need to check is that at the ABS module you have a voltage on both wires and when added up they come to 4.8-5.1V or so.

[VAskodas]

6 hours ago, ApertureS said:

Saying power and plug are okay doesn’t help much, what actual checks were done for the power supply and what was the outcome of this test.

 

as In, what pins were checked using what tool and what was the output reading in what state was the car.

 

was the ground load tested and on what pins?

 

Regarding the canbus - you’re looking into that too much without doing the basics and the above checks first. If there was a short to ground or to the other can wire you’d have no comms with a lot of other modules or it would be running in 1 wire mode. For the canbus all you need to check is that at the ABS module you have a voltage on both wires and when added up they come to 4.8-5.1V or so.

Well, i firstly checked the power feed from the fuse box to the abs module plug. (Obviously the fuses were checked first). I’m getting 12.4v on the abs plug  (the 2 thick wires of the plug and the ground that I can’t remember the pin number).

I can’t tell if I know how to load test any component so there is that. 
 

The state of the car during measurements was engine off ignition On. All measurements were taken with the same digital multimeter. 
 

As for the canbus wires, I will check them today. 
 

note: cats are having good time using my engine bay many times so one thing I’m thinking is the possibility of some damage made by the visitors. 

[VAskodas]

SOLVED!!!

There was a bad ground connection of ABS module in engine bay. The bolt was rusty and painted. Also there was a plastic ring between the nut and the bolt and some damage to the ground cable. I removed the plastic ring, remove every rusty spots, gave a little twist to the cable so the remaining wires can connect better to each other and voila!!!

 

My initial measurement on the ABS plug wasn’t proper. I didn’t check the ground of the plug (pin 13), just measured the power feeds with another ground point. My bad!!!

 

I will post some pictures about the finding. 

 

Anywho, thanks for the input. I hope this case will help others too. 
Bye. 

[J.R.]

Well done, people have been taken for loads of money unnecessarily for the same problem.

On 18/03/2024 at 22:17, ApertureS said:

First thing will always be check for:

power at the module plug

a good ground that is load tested not just resistance check

then look for your voltages on the canbus wires

 

If all of this tests okay, then you are looking at a failed ABS module.

 

Spot on once again! 👍

[ApertureS]

This is where a load test comes In handy.

 

a simple resistance check would have shown 0 ohms resistance as its only pushing a very small current through the system and would be signed off as okay.

 

The trick is to connect a (fused) H7 55W bulb to the circuit and power it from the battery and via this ground wire. That way a much higher amperage is being pulled which would strain the circuit and a measured voltage drop would tell you the resistance is way too high when the circuit is loaded up.

 

a single strand of wire still connected would pass the first test but fail the second  

[MarkMcG]

I'm having this problem now with the same symptoms. Octavia vrs tsi 2015.

Looking at your picture I don't have an earth at this location. I've checked the battery and getting 14.6? Vaults whilst idling and 12.6/7 when off so fair to say alternator and battery OK. 

[VAskodas]

4 minutes ago, MarkMcG said:

I'm having this problem now with the same symptoms. Octavia vrs tsi 2015.

Looking at your picture I don't have an earth at this location. I've checked the battery and getting 14.6? Vaults whilst idling and 12.6/7 when off so fair to say alternator and battery OK. 

Same issue as we say you cannot connect to ABS module at all? Did you use any scanner to read the codes and you cannot connect to ABS module? If so, try to follow the loom from the ABS module and see if there is a brown wire connected to vehicles chassis. 
 

give more info of what steps you performed. 
 

[MarkMcG]

U0121, I have 2 x scanners but not vcds. 

Because it can't communicate with abs it has caused a lot more issues I.e usual steering light, tyre pressure, engine management etc. I have removed the 2 x rear abs sensors this evening and carried out resistance test and they are OK. I still can't rule out the front 2. I'll have a look at the loom for abs pump tomorrow evening when i get a chance. This is under battery area I think and will update you once I get more time  

[VAskodas]

8 minutes ago, MarkMcG said:

U0121, I have 2 x scanners but not vcds. 

Because it can't communicate with abs it has caused a lot more issues I.e usual steering light, tyre pressure, engine management etc. I have removed the 2 x rear abs sensors this evening and carried out resistance test and they are OK. I still can't rule out the front 2. I'll have a look at the loom for abs pump tomorrow evening when i get a chance. This is under battery area I think and will update you once I get more time  

OK, this is very similar if not exactly the same problem i was experiencing 2 days ago. First, check for blown fuses of the ABS system in the engine compartment fuse box located at the right top (the 2 big ones. green fuse 40A, blue fuse 20A). Check also for voltage present on the fuses. If you can pull the fuses off and check the pins for each fuse for supply  voltage (one of the pins has to have voltage). If everything is OK, then pull off the ABS module plug and measure for voltage on the big pins of the plug (it must be 2 power feeds). Also, check the continuity of the ground pin that is the pin number 13, on my plug at least (check for diagrams of you specific vehicle to be 100%)

Last but not least, upload pictures of your engine bay , the ABS module and the ABS plug.

[VAskodas]

Any updates Mark????? Did you solve your issue?

[MarkMcG]

Hi, checked both front abs sensors and they are OK. Haven't checked reluctor rings as they are hidden.

I have checked all fuses  under bonnet and behind glove box, no issues. 

I have 4un out of time as the car is booked into a skoda dealer tomorrow and we need it back on the road. It pains me to hand it over as imexpecting my pants to be pulled down. I'll update once I know more 

[VAskodas]

1 minute ago, MarkMcG said:

Hi, checked both front abs sensors and they are OK. Haven't checked reluctor rings as they are hidden.

I have checked all fuses  under bonnet and behind glove box, no issues. 

I have 4un out of time as the car is booked into a skoda dealer tomorrow and we need it back on the road. It pains me to hand it over as imexpecting my pants to be pulled down. I'll update once I know more 

Well, good luck then. I hope for once the dealer makes it right and will not, as you say, pull your pants down

Did you prepare  yourself to pay for a new ABS module if they say so?

If not, get your ride back home and update the topic. I would like to assist you finding the fault. I'm very positive that it would be a loose ground connection somewhere in your engine bay, specifically the one of the ABS module.

Anyway, good luck.

[J.R.]

On 23/03/2024 at 21:16, MarkMcG said:

I have removed the 2 x rear abs sensors this evening and carried out resistance test and they are OK.

 

3 hours ago, MarkMcG said:

checked both front abs sensors and they are OK

 

A resistance check does not confirm that a wheel speed sensor is operating correctly, it may indicate one theoretical failure mode and it may well tell you that your new pattern part one is not going to  work because it has the wrong resistance but by far the major failure mode of these sensors is a fractured internal sintered magnet, the only way to diagnose whther they are functioning correctly is via VCDS or using an oscilloscope.

[VAskodas]

9 minutes ago, J.R. said:

 

 

A resistance check does not confirm that a wheel speed sensor is operating correctly, it may indicate one theoretical failure mode and it may well tell you that your new pattern part one is not going to  work because it has the wrong resistance but by far the major failure mode of these sensors is a fractured internal sintered magnet, the only way to diagnose whther they are functioning correctly is via VCDS or using an oscilloscope.

I believe this is just a step that Mark did just by following some online instructional videos or similar. The problem he has is  that he cannot able to connect to ABS module at all. I think even if some of the sensors are bad you should still can connect to the ABS module but he can’t. 

[ApertureS]

11 hours ago, MarkMcG said:

Hi, checked both front abs sensors and they are OK. Haven't checked reluctor rings as they are hidden.

I have checked all fuses  under bonnet and behind glove box, no issues. 

I have 4un out of time as the car is booked into a skoda dealer tomorrow and we need it back on the road. It pains me to hand it over as imexpecting my pants to be pulled down. I'll update once I know more 

Why are we focusing so much on checking wheel speed sensor resistances?

 

Do as I suggested in my first post - you need to be checking at the abs module for power, a load tested ground and canbus voltages.

 

Checking specific components (and not fully) on the abs system is not going to help you find a non connection to a module sorry.

[MarkMcG]

Wee update on this, had the car back this evening and repaired. New abs module at a considerable cost. It is what it is. I checked for bad earth before it went in and couldn't find anything.  All fixed now, hope it isn't common on these cars

[VAskodas]

43 minutes ago, MarkMcG said:

Wee update on this, had the car back this evening and repaired. New abs module at a considerable cost. It is what it is. I checked for bad earth before it went in and couldn't find anything.  All fixed now, hope it isn't common on these cars

Well at least you got your car back and running. That’s all that matters I guess. Just hopped that we could help you more with this so you could fix it yourself…..

[MarkMcG]

I know, thanks for the guidance. I'll be purchasing a vcds cable to be able to diagnose and code parts myself in future if needed 

[VAskodas]

1 minute ago, MarkMcG said:

I'll be purchasing a vcds cable to be able to diagnose and code parts myself in future if needed 

It’s a good start. The internet is full of how to’s and informations about VCDS so it’s safe to say that you will be covered on any issue. I’m using OBDeleven and I’m also covered about pretty much everything I want related to finding a fault or just activating and deactivating stuff in my car. 😉

For example, my last mod was to activate hill hold (hill assistance) and deactivating engine start-stop function permanently.