Over sensitive ESP?

[EuroSag]

Another problem has been identified today. When accelerating hard in 2nd or 3rd gear, the ESP light keeps flickering on and reduces the power accordingly - even though its on a perfect bit of straight, dry tarmac.

Had somebody look at the vag-com for me and under the Brake ABS category it was all clear. There was some faults with the gas temp sensors, which is also reducing power, but could this also affect the ESP?

Having spoken to a number of people, no one appears to have heard of over sensitive ESP before.

Anybody got any idea's?

[Nige_RS4]

Could be a blocked / failing ABS sensor - there was a post on this a while back, seem to remember it was something to do with the sensor ring on the driveshaft or something like that. First stop would be to check all sensors I guess?

[EuroSag]

Thanks mate. I've got it going into Audi on Tuesday, but what's the likelyhood they'll just reset the ECU and tell me everything is ok

[SimonS4MTM]

High!

I think it is a big job to look at the sensor rings in the CV joint.

[EuroSag]

Ahhh, its at times like this that I'm happy to have a piece of paper saying Audi warranty until 2007.

[EuroSag]

I've just had a look on another forum and some guy had a similar problem and it was diagnosed as a duff MAF sensor. Does this sound feasible to you guys?

[SimonS4MTM]

Unpluging the MAF does cause the light to come on the dash IIRC.

[SimonS4MTM]

Though I doubt it would cause the ESP to operate. More likely to be your abs sensors

[Golich]

HHmm odd one - Are you sure its not the EPC light that is flickering?

Have you tried switching off the ESP?

I'm told the ESP system monitors accelerometers in combination with steering wheel angle and indivdual wheel rotation. So perhaps it is monitoring straight-line acceleration and confusing this as a corner and you are out of control and therefore cutting power? However, I would have thought if that were the case, it would apply a combination of front and rear brake.

As mentioned the other way the ECU is programmed to cut power is wheel slip and this of course is interpretted from the output of the sensors at all 4 hubs.

The sensors are pressed deep into the hub and sensor ring is attached to the CV joint also deep into the hub. You can't really see either from a simple inspection. You would have to loosen each driveshaft bolt to see the ring and I don't think there is enough axial movement in the CV joints to get them all the way out of the hub to see the surface of the ABS sensor without dropping one of the main suspension ball joints.

For what its worth - in my experience of other cars a faulty wheel sensor throws a constant ABS light.

Faulty exhaust gas temp probes can have a significant effect on the performance and won't always throw an error code. Mind you from first hand experienence of replacing 4 to date (2 on my S4 and 2 on my RS4) none of them set the EPC light off either.

In both the S4 and RS4 only one probe reported an error while the other which was also defective reported nothing. The clue came from monitoring its output which was erratic.

[TarmacTerrorist]

Cant remember exactly why I did it now but I had the same issues after putting different set of tyres on the front of the car to that on the rear ( it was only a temp thing iirc) soon as I got all 4 back on the same rubber it went away..

Are you using matching tyres??

[EuroSag]

How weird is that! As it happens I do have Dunlop's on the front and Michelin Pilots on the rear, I wonder if this could be the problem? Trouble is both sets of tyres have loads of grip, so it could be an expensive and pointless exercise if I was to change them.

I have switched ESP off and the problem is significantly reduced, however, there is still an intermittent issue with reduced boost - but this might be due to the faulty Gas Temp sensors that need replacing?

Just another note, when the ESP light flickers on and off it doesn't seem to be applying the brakes, rather just reducing the power/boost.

It gets stranger by the minute

[TarmacTerrorist]

DEFINATELY!!!!!


Get them changed asap!!! I could also feel transmission wind-up coming through the car (what you may perceive as reduced boost!!!) do not delay do it today.

p.s I would get shot of the the 9000 piles of dunplops and stick with teh michies.

[EuroSag]

Yep the Dunlop's are a pile of poo and were on the car when I bought it. Not for much longer though - Monday morning they are coming off!! Thanks for the help mate, i'll let you know how I get on.

[TarmacTerrorist]

yes please do

[ConvictS4]

I had both issues on my B5 S4.

On the EGT's - get them replaced.

On the ESP - I had same flickering problem - I also had differing tyres front and rear - swapped them to all matching, had the ABS and road speed sensores cleaned (they were very dirty after new brake pads) and the other sensors (yaw and steering ?) reset. Now all fine.