[jethari]

I have a 2011 Vento petrol automatic. All of a sudden I've started having this problem: As I start driving, the speedo needle starts flicking up and down. When this happens, the auto transmission also goes haywire and does not shift up with increasing rpm. After some time, the ABS fault comes on. From this point onwards, the speedo behaves normally as also the auto transmission. Tried scanning with Torque Pro, but no fault codes are latched. Can someone throw some light into this?

Thanks
Hari

[vikram_d]

From the top of my head I think it could be a problem with either the vehicle speed sensor in the gearbox or wheel speed sensors of the ABS unit.

[jethari]

From what I have managed to glean from the net, it is safe to drive with the ABS fault light on. Normal power assisted braking is available, only the skid protection is not available. However, it is not recommended to continue with this condition for long.

An update, today when I turned on the ignition, the speedo needle started flicking up and down (with the engine off), ABS light went off after the self test. Started the car and moved off, the speedo kept flicking up and down intermittently. After a few minutes, the ABS light was triggered. After this, the speedo needle settled down to normal indication, full braking was available. I'm still trying to figure out if the vehicle speed sensing system and the ABS are somehow interconnected.

Hari

[jinojohnt]

The main component that is common between the odometer and ABS is the wheel speed sensor. Since both ABS and speedometer are showing problems, your first point of check should be the wheel speed sensor. First send your car for a thorough wheel wash (light pressure wash and dry), because mud is known to create issues for the wheel speed sensor.

[jethari]

Originally Posted by jinojohnt

The main component that is common between the odometer and ABS is the wheel speed sensor. Since both ABS and speedometer are showing problems, your first point of check should be the wheel speed sensor. First give your car for a thorough wheel wash (pressure wash), because mud is known to create issues for the wheel speed sensor.

Thanks for the tip jino. It is the monsoon season in Mumbai and we have had plenty of rain this year with the related puddles and slush. I will straightaway give the underside a pressure wash and see what happens.

Hari

[crdi]

If it is the wheel speed sensor, which probably it is, you can thank your stars that the thing is not astronomically priced. The hitch however is that each wheel has one and they are known to perish in 4-5 years of use, especially of those cars used frequently in slushy conditions.

[Sankar]

If the ABS light is on it could be the wheel speed sensor. Replaced that in my friends manual vento's rear wheel for 4K. Cleaning didnt work.

Also get a vcds scan done before you do anything, many codes will not be picked up by a generic OBD scanner and app. If you dont have access to vcds get the scan done by dealer and be there so that you can check yourself all the error codes present.

[jethari]

Update: did a scan with VCDS and it shows up right front wheel speed sensor. Will be taking it in for replacement. One other thing I discovered, Torque Pro only reads engine and transmission codes. It does not access the other controllers (I was trying to look for fault codes using Torque Pro earlier).

Hari

[jethari]

Update 2: Replaced the right front speed sensor. Been driving for almost a week now, no faults. Thanks for all the help and suggestions.

Hari

[mmridul]

Over this past weekend, my car developed some strange issues:

1) First my speedometer started fluctuating wildly, as if it were possessed, even though the car was completely stationary
2) Then, on my drive back home, the car suddenly lost all power during my gear shift. It was electrically alive, but the engine seemingly refused to follow the accelerator
3) Then, the car shuddered and the ABS light came on

The following morning, Sunday September 15, I got my car towed to the nearest VW workshop (Autobahn Volkswagen, Jogeshwari near Ram Mandir). Today upon speaking to the service adviser, he informed me that one of the ABS sensors is bad, and told me that all 4 would fail soon and hence I should change all of them for "safety reasons". Upon being told that my car is under extended warranty, his tone suddenly changed, and he would change only the affected sensor.

https://youtu.be/x4y8NhJwpNs

This was only a sign of things to come. Upon asking for the proposed resolution of the other two items, he informed me that since they are unable to diagnose the issue, they would not be attending to the same, even though video proof was present in the case of the speedometer. In his opinion, the faulty ABS is to blame for all the issues, including sudden loss of power and faulty speedo.

Note, the car is a Polo GT TDi (Dec 2014 manufactured, Jan 2015 registered), and it us under its 5th year of extended warranty.

I am not sure how to proceed, and wanted your views on whether a faulty ABS can cause some or all of the issues faced by me.

[dark.knight]

Has the faulty sensor as "diagnosed" by the technician been replaced by VW under warranty? Have the problems surfaced after that, or are you preempting your moves?

I think it'd be wise not to jump to worst case, scenarios and take it one step at a time, get whatever parts as deemed necessary by ASC, replaced under warranty, drive around for a week, if the speedo still fluctuates and if there is power loss, then go back to them for the next round of troubleshooting.

As far as I know, and in a simple car layout, the ABS sensor should have zero bearing on the speedometer itself, though it can cause some symptoms of brake jamming/locking or incorrectly activating depending on the type of sensor failure, and if that in turn affects your driving then the speedo will of course, show drops in power.

In your case the speedo was wildly fluctuating when the car was in idle, I'd say follow the ASC's suggestion as long as its covered, if the problem is solved, well and good. There seems to be both mechanical (part-related) and electrical (signal related) problems involved, but I'm only winging it, to get an accurate answer you need to ask VW for the fault codes when they scanned the ECU (always do that), so that you know that they aren't making stuff up.

Since they've given their solution, I'd recommend you go through with it (get them to give a snapshot of the ECU scan) and keep all paperwork ready should that not lead to absolute resolution.

[anoop.u]

Yes, this can happen and i have experienced this first hand.

After going through 6 ABS sensors (VW Polo) in the past 4.5 years, i can say for sure that this has a 90% chance of being related to your ABS sensor.

When my first ABS sensor went kaput, the following sequence of events occurred:

1. Steering went hard
2. Some sort of clinging noise from under the car, as if the under body took a hit
3. Brakes went hard / heavy noise upon braking.
4. ABS light came on.
5. The car went back to normal after shut down and restart (ABS light still on).

I rushed to VW, got the faulty front right sensor replaced only to face the same issues within the next 140kms. When i took it in, they diagnosed the front left as faulty and repalced it.

Once the speedo also started fluctuating showing inaccurate readings (40kmph when i was under 20).

I would suggest you to get the faulty ABS sensor replaced ASAP. VW wont agree to change the non-faulty sensors under warranty.

But be mentally prepared to get the pair sensor also replaced within the next 100-200kms as chances are it will also fail.

Regards,
Anoop

[SCORPION]

Some speedometer designs use the wheel speed sensors for the speedometer and for the ABS. A faulty sensor can therefore give you erratic speedometer readings and an ABS warning light.

However, with my limited knowledge, I cannot see how a faulty ABS sensor can cause the engine to lose power or shudder. There is probably another electrical issue and therefore, another faulty sensor feeding wrong engine parameter data to the ECU.

I would advice everyone to invest in a decent OBD II diagnostic device for situations like this. It's a one time investment and can save you several thousand rupees if the ASC decides to take you for a ride. Error codes can be decoded on the net. Even if you are not be able to diagnose the entire depth of the issue, you will at least know roughly where the problem lies, and if the ASC or workshop is trying to cheat you. You can even give the error codes here and the experts may be able to give much better advice based on the error codes before taking your car to the workshop.

Originally Posted by anoop.u

1. Steering went hard
2. Some sort of clinging noise from under the car, as if the under body took a hit
3. Brakes went hard / heavy noise upon braking.
4. ABS light came on.
5. The car went back to normal after shut down and restart (ABS light still on).

The power steering system provides the hydraulic pressure for the brake booster assist system and it is possible that a faulty ABS sensor can indirectly affect the power steering system. When the ABS activates, even under normal circumstances, you will hear a gravelly, metallic kind of noise.

I think a poll is inappropriate for something like this, where there is a definite answer and not just opinions or personal choice. If you do want a poll, may be you should edit the poll title because I wanted to say 'YES' for speedometer fluctuations and a 'NO' for power loss.

[RJ2285]

I have experienced something similar in my 2014 December manufactured and Jan 2015 registered POLO GT TSI.

Is it fair to conclude that VW cars should not be taken out of the city after 4-5years, for long drives with the fear of these sensors going kaput anytime!

[nalinsaxena23]

I faced this strange thing today morning in my 2015 Vento TSI (done 45000 kms). Was driving out of my society at speed of about 10kmph, in first gear (transmission in manual mode). Applied brake to reduced speed when suddenly ABS kicked in (no wet surface). Then suddenly speedometer needle started flickering similar to how other members have reported. I was stationary and still speedometer showing speeds of 40, 60 and even 100. No ABS warning light in my case.

I turned off the vehicle and started again, no issue thereafter.
Still as a precautionary measure, took it to VW ASC to get it scanned. To my horror, the error code detected is "P073F unable to engage 1st gear (intermittent)".

Its actually a surprise because car is behaving just normal, no transmission jerks what so ever. 1st gear engagement is also not an issue at all.
The issue just happened once.

Requesting experts to guide on steps I need to follow. Thanks in advance.