# ESP light on update...



## anthony_m (Aug 28, 2008)

hi all,
well, i have just checked the car to see if i can see any obvious reason for the ESP light to be on continous and have discovered that the cooling fans are running even when the engine is cold, if you turn off, and just turn on the ignition without firing it up, the fans are off!!! is this normal? or could this be linked to the ESP fault? the engine temperature is fine when hot, and the coolant level is constant, ie, no leaks, or overheating signs. 
untill i get some software to diagnose the fault codes [by the way where can i get the necesary kit for doing this] i am a bit out of my depth, i am used to working on conventional systems having been an old school mechanic and engine builder [many years ago now]  anyway, any help with this would be much apreciated guys.
anthony...


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## anthony_m (Aug 28, 2008)

just a thought,
i have recently changed the rear brake disks and pads, and had to remove some of the brake fluid from the resevoir to prevent it over flowing when winding the pistons in on the calipers to fit the new pads, so brakes were obviously desturbed, could it be a brake sensor switch or am i barking up the wrong tree completely! just thought i would give you guys as much info as i can...


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## eightfoot (Dec 24, 2007)

anthony_m said:


> hi all,
> well, i have just checked the car to see if i can see any obvious reason for the ESP light to be on continous and have discovered that the cooling fans are running even when the engine is cold, if you turn off, and just turn on the ignition without firing it up, the fans are off!!! is this normal? or could this be linked to the ESP fault? the engine temperature is fine when hot, and the coolant level is constant, ie, no leaks, or overheating signs.
> untill i get some software to diagnose the fault codes [by the way where can i get the necesary kit for doing this] i am a bit out of my depth, i am used to working on conventional systems having been an old school mechanic and engine builder [many years ago now]  anyway, any help with this would be much apreciated guys.
> anthony...


fans will run all the time if the a/c is on,is your'e maf conector pluged in correctly


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## anthony_m (Aug 28, 2008)

hi,
air conditioning was on when i looked so, that takes care of that question, as for the maf connector, well, seems to be ok, its probably a daft question but why would this affect the ESP??? :? 
thanks, anthony.


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## volkswizard (Mar 8, 2006)

The ESP gets a torque calculation from the MAF and thus MAF faults disable the ESP as any incorrect calculations could cause ESP to malfunction.
I was working on an A3 1.8T last week, went for a test drive and ESP light came on.
VAG COM'd it and came up with 'MAF sensor error, reading too low' - Easy to blame the MAF but there was an air leak so unmetered air was getting into engine. ECU was wondering how come more air than the MAF had measured was getting in and thus ESP light came on as it assumed a MAF faults - ECUs aren't clever enough to work out that there is an air leak!


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## anthony_m (Aug 28, 2008)

volkswizard said:


> The ESP gets a torque calculation from the MAF and thus MAF faults disable the ESP as any incorrect calculations could cause ESP to malfunction.
> I was working on an A3 1.8T last week, went for a test drive and ESP light came on.
> VAG COM'd it and came up with 'MAF sensor error, reading too low' - Easy to blame the MAF but there was an air leak so unmetered air was getting into engine. ECU was wondering how come more air than the MAF had measured was getting in and thus ESP light came on as it assumed a MAF faults - ECUs aren't clever enough to work out that there is an air leak!


hi volkswizard,
thanks for the explanation, very interesting and i now have a better understanding of how the system works, i will check all pipework this week and see if there are any obvious leaks, any ideas on the most import areas to check?
once again,thanks very much for your help on this, much apreciated...


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## anthony_m (Aug 28, 2008)

hi all,
well, just come back from taking the car into a diagnostics center, and apparently there are no fault codes logged! the only thing the guy there could come up with is that the wear indicators on the front brakes could be causing the ESP system fault, anyone heard of this? :? 
anthony...


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## funkybluecheese (Aug 6, 2006)

anthony_m said:


> hi all,
> well, just come back from taking the car into a diagnostics center, and apparently there are no fault codes logged! the only thing the guy there could come up with is that the wear indicators on the front brakes could be causing the ESP system fault, anyone heard of this? :?
> anthony...


Maybe your ESP issue is related to the brakes, although I'd like some confirmation from someone knowledgeable...

Both my ESP and ABS lights came on a month ago, followed by the brake pad warning light a couple of weeks after. Initially they would flicker on and off, creating a weird 'lumpy' braking sensation and a slight loss of power in one instance.

My TT's up for its service/MOT Friday, and I'm well aware the brakes are on the way out... I'll let you know if this colourful array of warning lights disappear!

Meanwhile, does anyone know how many 'safe' miles are left on average when the brake pad light comes on? I've done about 500 miles since it first appeared.


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## T7 BNW (Jul 20, 2008)

1000 miles from the brake light!

But i wouldnt advise testing that

I get mine changed before the light even comes on generally! Otherwise you need to replace the sensor!


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## anthony_m (Aug 28, 2008)

hi all,
well, i have just ordered a new set of mintex brake disks and pads for the front, to match the new disks and pads i have just fitted to the rear! hopefully this might solve it, i originally thought that when i changed the rears i may have disturbed something, or upset a sensor,but i made sure everything was straight and clean, i even checked the ABS sensors, and disks before putting the wheels on. i have had the car about a month now and between fitting new cam belt and related pulleys tensioners, water pump etc, oil and filter change, new rear springs, and now new brakes all round, its becoming a bit of an expensive hobby, i just hope that after this, i may get some decent mileage out of it!!! :roll:


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## anthony_m (Aug 28, 2008)

hi all,
the sarga continues, a friend of a friend has a 225 tt and her ESP light came on, so she took it to bridgend audi in wales, and all they did was replaced the battery and the ESP was back working normally! apparently, if the battery voltage drops below a certain limit, it will cause an ESP fault,,, seems feasable to me given all the sensitive equipment on modern cars these days.
anyone else heard this one, and if so, did a new battery cure it!


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## anthony_m (Aug 28, 2008)

hi all,
just checked the battery voltage with an acurate multimeter, and it measures 12.44 volt which is i feel more than adequately over the normal 12v threshold for everything to work normally, ohh well back to the drawing board as they say!!!


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## John-H (Jul 13, 2005)

The sensor for brake pad wear is part of the pads - it's just a wire end buried in the pad material that gets worn away by the disc. When you put new pads in the sensor is replaced in doing so.

If you were feeling the ABS kick in (pulsing back pressure felt in the pedal), then either you were on a slippy patch when braking, or if only lightly braking or on a good road, you could have an ABS sensor going intermittent. If it looses the signal the ABS system initially assumes a wheel has locked up. The ABS sensors are also used for the ESP and traction control. The ABS sensor fault is only stored for as long as the ignition is turned on - you'll need to keep it on to trace which one through diagnostics.

Magnetised dirt on the sensor can blur the signal so it's worth checking for iron filings or bits of magnetised debris stuck on there. Damage to the slotted sensor wheel can also cause a marginally weak signal. What tends to kill sensors is corrosion getting into the coil assembly - this can crush the coil and initially cause an intermittent temperature related short before complete failure.

The off load voltage of the battery is not the complete story. The battery should ideally be tested under load. If you have a weak cell the voltage can drop too low when starting and cause odd effects in the electronic modules.


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## funkybluecheese (Aug 6, 2006)

John-H said:


> The sensor for brake pad wear is part of the pads - it's just a wire end buried in the pad material that gets worn away by the disc. When you put new pads in the sensor is replaced in doing so...


Yeah, that supports the diagnosis the garage have just given me RE my issue (as detailed above). The sensor is the first to get it as the pad wears low, hence my ABS/EPS fault register, followed by a break pad warning. I also discovered I had 95% wear on the front pads! That's got to be some kind of record, surely.


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## anthony_m (Aug 28, 2008)

hi all,
well, i changed the front disks and pads last night, but on taking out the old pads i realised there is no wear sensors fitted to my car!is this because its an early one [1999] anyway that puts another idea to bed, john, i cleaned all the sensors and disks while i had the brake disks off.
i havent checked to see if the esp light is still on since it was late when i finnished putting the car back together last nigh, but i guess it probably is as i didnt find anything wrong!!!
thanks anyway guys.


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## Nick 225TT (Jun 6, 2008)

The esp or any other error will remain if it is stored in the ecu if you dont have a vag com then a battery disconect for 5 mins will clear any fault codes however have yor radio code to hand if you have a factory stereo :wink: 
If any fault remains the lamp will come back on soon enough [smiley=bigcry.gif]


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## anthony_m (Aug 28, 2008)

hi all,
well my ESP light was still on this morning while driving to the city, [no news there then] but, on my journey back i noticed there was something missing in the dashpod, yes, the ESP light was off!!! when i got home i fount that i can now switch the ESP button and everything seems to work as normal, yippee...  the only thing i can think is that it was down to the battery voltage being on the limit, and now i have been driving without the extra drain of the air conditioning on [colder weather] so the cooling fans are also off most of the time, the battery has had time to charge properly...what ever it was, i just hope it stays working...thanks anyway guys for all your sugestions, maybe my experience on this matter may help someone else with a similar fault in the future.
regards,anthony.


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## John-H (Jul 13, 2005)

It might be that you've cleared the fault but that the system needed two fault free ignition on cycles and correct signalling for the fault light to go out. It's like that if you disconnect the MAF. Anyway, I hope it stays that way for you  .


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## anthony_m (Aug 28, 2008)

John-H said:


> It might be that you've cleared the fault but that the system needed two fault free ignition on cycles and correct signalling for the fault light to go out. It's like that if you disconnect the MAF. Anyway, I hope it stays that way for you  .


thanks john,
and of course you may be right, i just hope it stays like it now!!!
regards,anthony...


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## anthony_m (Aug 28, 2008)

hi all,
well there has been another developement, while visiting a friend of mine who lives over the brecon beacons today, the esp light came on again, just as i was aproaching the highest peak, i stopped, turned off the ignition, then back on, and the light was out and stayed out for the remainder of the journey, on the way back, the light came on very close to the same spot as on the way up! it would seem then, that its an air pressure/density thing, so i suspect it could be the maf after-all, but what to do now... :?


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## boosted (Jun 3, 2007)

Get someone with VAGCOM to scan it.


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## anthony_m (Aug 28, 2008)

i have had it scanned once and no error codes showed up.. :?


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## boosted (Jun 3, 2007)

What did they scan? Just the engine, or each of the specific modules? i.e. ABS and 4WD


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## anthony_m (Aug 28, 2008)

hi,
as far as i am aware, they scanned all parameters and couldnt find any fault codes logged!
mine has had a new dashpod lately [within the last 4 months] but everything seems to be working fine except for this intermitent ESP fault.


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## cyberdude (May 24, 2002)

The haldex controllers are known to fail and they cause the ESP light to come on but you would normally see a fault code thrown up in VAG-Com. May be worth checking that the connector for the controller is clean and secure. It is in a area where it can get full of road crud.

A long shot but worth consideration.
Does the ESP light mostly come on when the car is cold, rather than when it's warm from just been driven?
One test you can try.
With the car cold, i.e. in the morning, try turning on the ignition without starting the engine and then listen for a sound near the rear axle that sounds like a servo motor hunting and ticking (don't confuse this with the buzz you may hear from the fuel pump which will be a constant tone). If you can hear a servo motor type sound and it doesn't stop then it's probably the pre-charge pump in the haldex that has failed. It won't do it when the car has been driven and is warm.

It may not do this everytime so do the check over a few mornings.


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## anthony_m (Aug 28, 2008)

thanks cyberdude,
i will check for this and let you know my findings, but at the moment it seems to do it after i have driven a while, as stated,for a while i couldnt get it to go out it was on constantly, but after changing the disks pads all-round, after a while, the ESP light just went out, and stays out now most of the time... :? 
anthony...


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