S3 (02) rear wheels lock on right/left turns

**thegoal007** · 30-01-2009,12:07 PM

Here's a strange one, or maybe not so strange, sometimes when turning tight corners or 3 point turns (not in straight line) it feels like the back wheels get dragged and 'lock-up' briefly. I've even had it when I have gone round sharp roundabouts and I could feel it hapenning and seen the esp light flash briefly. It certainly worse when cold, but does happen frequently during summer too. Car is and has been completely standard on 17" from new. haldex oil and filter are changed regular. Rear brakes/handbrake all replaced.
The Audi diags is showing no errors whatsoever.

Basically I found what controls the ESP system is 2 things:
the rear diff control unit
the abs/esp unit

Anyone experienced this problem ? One person I've managed to contact who had the exact same problem said the ESP control unit fixed his problem after changing many parts, such as the rear controller unit and the diff itself. His too was showing no error codes anywhere !

When Audi do there diags do they only plug into the ESP unit ? How does the rear controller get checked out independantly or may it doesn't becuase it all feeds through the main ESP unit ?

Another thing to note is even if I press the esp button to switch it off - the light comes on in my dash, but the problem is still there ! It's as though it is permanetely on - doesn't help me getting any closer to solving this because the fault could lie in either place and not really willing to fork out to 'potentially' replace both units ! The other issue is that it is not hapenning all the time. This morning everything was perfectly OK from a cold morning start, but 2 miles away when I went to park the car it was quite bad and when leaving an hour after that.

https://www.vwaudiforum.co.uk/forum/s...hlight=locking

**S3 beast** · 08-02-2009,10:42 PM

Im unsure of your problem and i will be awaiting to see if someone can help you as this is an interesting issue.. im sure someone on here will be able to help.. if you do find out away from this forum will you do a post please

**ed'sA3-1.8THK** · 09-02-2009,09:30 AM

your s3 has (1) abs magnetic/inductive pick-up and (1) esp magnetic/inductive pick-up mounted at each wheel backing plate

single 5mm sockethead screw

DO NOT disconnect any electrical connects - at each wheel individually remove sensor body from backing plate/splash guard & use dry clean paint brush to brush away iron/magnetic debris from pole gap (sometimes alot of dust will collect - DO ALL SENSORS in this manner

if problem continues the abs/esp control module/board is defective and must be replaced

early models are possible re-soldering candidates, while recent design revision modules simply can't be hand soldered...

one caveat, I assume you are certain that your rear brake hoses have not partially collapsed (internally) preventing fluid return AND your rear calipers are working correctly w/o corrosion causing piston drag on pistion seal ring resulting in delayed release of rear brake(s) resulting in uncontrolled rear slides...

if my car, I would be concerned (for safety of others)... needs fixing

**thegoal007** · 09-02-2009,07:42 PM

I'm failry sure the rear calipers are not a problem. I'm not experiencing uncontrolled rear slides. When the esp light flashes on tight corners I'm not braking at the time. There are no problems braking in any direction. the locking of the rear wheels is when attempting sharp turns - regardless of braking.

I'll see to the other points you mention with regard to cleaning the sensors. Just wondering why nothing is showing up as faulty on the ecu ?

**A3_FSI_2.0** · 09-02-2009,07:56 PM

just because your not pressing the brakes, doesnt mean the ESP is not doing it for you believing its helping you control the car. With that said though, you say it still does it when the ESP is switched off.

TBH, to me it sounds a bit like the rear diff is locking up momentarily.

**thegoal007** · 09-02-2009,11:33 PM

yes, well I suppose that is true.

but it only does it when the sterering is excessively turned left or right (forward or reversing) whether I am at crawling speed, in which case the esp light does not flash, but the wheels feel seems to lock and then jump. At slightly faster speeds there is a light flicker of the esp light and you feel the same thing happening at the rear albeit a slightly different sensation - even at these speeds and ground/tyre conditions there is no reason for the esp to be cutting in. On straight lines there is never a problem. hence why I don't believe it to be a rear caliper/brake problem.

The only other guy to experience the same issue said he resolved his problem with a new ecu. Audi would say the rear haldex controller (?). I just wondering how common is this problem and who else has seen this specific problem?

If I follow the Audi route there's £600+ spent and if they are wrong into a new ecu - another £800 !!!

**ed'sA3-1.8THK** · 10-02-2009,02:28 AM

also there is the steering angle "rate of change" (yaw) sensoring of esp permitted map values - located underneath steering wheel

you may be overlooking point made by gentleman above - esp system functions autonomously/independently of driver inputs @ steering/accelerator/brakes AND can be Very Unpredictable if malfunctioning

You can't "Turn-Off" esp system...

on-board internal self-diagnosis monitor sub-routine/app of instruction set will perform condition review to determine functional/operational status of esp system (entire system) AND deactivate if anything found faulty... only manner esp is "turned-off"...

otherwise fulltime background system of canbus chassis

you have serious problem with your s3

one last caveat - ESP & equivilant stability systems rely on (4) equal "rolling diameter" tires - are all (4) tires of same rolling diameter, w/o (1) or more significantly different?

esp works v. well when same size/same manufacturers tires are fitted (wear related size!) - I am only aware of (1) case were severe tire belt runout mimiced smaller tire diameter & esp faulted as result

**ed'sA3-1.8THK** · 10-02-2009,04:21 PM

goal007,

there is issue with battery vent vapour corroding fuse block located on top of battery AND the small & large earth/ground threaded posts under battery tray = all must be inspected & if primary earth cable center lug area badly corroded, replacement is mandatory to prevent engine bay fire...

what most do not know is that abs/esp control & hyd pump module draws primary elec power from one of the fuses located on top of battery

if you have flashing or intermittent warning lights, inspect all circuits & earths in battery zone - this type of fault will not generate error code...

many vag chassis involved with this issue of earth/fuse corrosion a3,a4&tt )fwd definitely, but also some quattro models and of course corresponding vw models having similar chassis/layout

do give this your saturday morning - than it's down to abs/esp electronics module...

**Crasher** · 10-02-2009,04:28 PM

It’s a Haldex unit problem, it may show up on a fault code read.

**thegoal007** · 10-02-2009,05:36 PM

ed'sA3-1.8THK, replaced the battery about a month ago checked the whole area and no sign of corrosion.
I don't have any flashing or warning lights on my dash - only the esp light flickering when the locking feeling occurs at speeds - as I explained, but I presume that is correct.

Wheel locking aside, I have also noticed the esp light flash briefly on rare occasions when going over big potholes. my understanding is that this is 'quite correctly' showing me when the esp is cutting in (?).

What is the purpose of the esp button , if it's not to switch it off ? When I press it , the esp light on the dash lights up - so what is that telling me ?

crusher, it certainly sounds like a haldex unit problem - but as I have found out the haldex unit is also sent data from the main ecu and also (from reading replies in this forum) from various sensors. So it may not be the unit itself, if that is what you were implying (?)