Automatic Stability Control 99 528i - Replacing control unit
Discussion
A BMW specialist has diagnosed my ASC fault (blinking light every once and a while when accelerating hard) as the control unit (I believe the control unit also works the ABS). Cost of new part £600+. Cost of second hand part £90 through Parts Gateway. The specialist have refused to fit a second hand part and have said that most other garages with the necessary software to reset the equipment will do likewise. Am I really left with no other option than to pay for the new unit?
How specialist is such a job? Would I be wasting my time ringing around local 'all makes' garages?
How specialist is such a job? Would I be wasting my time ringing around local 'all makes' garages?
kevinpsw said:
A BMW specialist has diagnosed my ASC fault (blinking light every once and a while when accelerating hard)
For give me for potentially sounding very thick but surely thats what ACS does? You accelerate hard, ASC detects and deals with wheelspin, and the light blinks to inform you that the system intervened?Every BMW I have ever driven with DSC (the replacement for ASC) has performed in this way.
[TW]Fox said:
kevinpsw said:
A BMW specialist has diagnosed my ASC fault (blinking light every once and a while when accelerating hard)
For give me for potentially sounding very thick but surely thats what ACS does? You accelerate hard, ASC detects and deals with wheelspin, and the light blinks to inform you that the system intervened?Every BMW I have ever driven with DSC (the replacement for ASC) has performed in this way.
The light blinks and the system affects the engine's performance (a loss of power) when it really shouldn't. I'm talking about normal driving on good stretches of motorway in dry conditions going in a straight line. The control unit is reportedly sending nonsense signals (so the BMW specialist says and they initially said the blinking light was normal). I suppose I could just switch the system off but I don't like to just let things go on the car.
Sure it couldn't be worn tyres?
It doesn't sound like a major failure though (its only partial), and if the ASC on your 528i is anything like that in my 318iS of the same year, then its probably not even worth having it switched on in the first place.
Actually, thinking about it - its more likely to be the sensors that are at fault than the actual unit though. The various senders are generally in relatively inhospitable locations around the rear end of the car, and they're way more likely to fail than the electronic gubbins.
It doesn't sound like a major failure though (its only partial), and if the ASC on your 528i is anything like that in my 318iS of the same year, then its probably not even worth having it switched on in the first place.
Actually, thinking about it - its more likely to be the sensors that are at fault than the actual unit though. The various senders are generally in relatively inhospitable locations around the rear end of the car, and they're way more likely to fail than the electronic gubbins.
The ASC system uses the ABS sensors to detect slippage. If the ASC kicks in then it backs the engine off slightly to regain grip.
If the ASC kicks in on a dry motorway, then it is almost certainly an ABS sensor fault. It could either be a dirty connection, a faulty ABS sensor, a dirty ABS sensor or a dirty reluctor ring on the hub.
Its very rare for the modules to fail or kick up intermittant errors.
Have you every noticed any odd behaviour from the brakes? For example, a tendency for the ABS to kick in just as you come to a halt.
If the ASC kicks in on a dry motorway, then it is almost certainly an ABS sensor fault. It could either be a dirty connection, a faulty ABS sensor, a dirty ABS sensor or a dirty reluctor ring on the hub.
Its very rare for the modules to fail or kick up intermittant errors.
Have you every noticed any odd behaviour from the brakes? For example, a tendency for the ABS to kick in just as you come to a halt.
It shouldn't be tyres, they are all quite new. I have not noticed any odd behaviour from the brakes.
Wheel sensors were exactly what I thought. Apparently, however, the codes thrown by the diagnostics say it is the control unit. I would like to think that the garage is not trying to pull a fast one but I suppose a second opinion might be worth a try.
Wheel sensors were exactly what I thought. Apparently, however, the codes thrown by the diagnostics say it is the control unit. I would like to think that the garage is not trying to pull a fast one but I suppose a second opinion might be worth a try.
Edited by kevinpsw on Tuesday 9th October 12:16
Edited by kevinpsw on Tuesday 9th October 12:18
Evening all!
The early E39's to about '99 had an issue with sporadic ASC intervention.Quite often this would leave NO fault codes in the memory.
As long as the tread depths are even ie 4mm all round not 2mm rear 6mm front,and it is proven the wheel speed sensors and reluctor wheels(sensor pick up) are good and so on then the Control unit is the way forward-but thats as long as it has been fully diagnosed.I cant say for definate as I havent seen it.
The control unit is easy to fit.....4 torx 20 screws,no bleeding or removal of actual hydraulic unit needed.You must ensure the area is clean first-ie no mud.
In an ideal world you should,to ensure a long term fix buy the new unit and then encode it with the BMW SSS system.
But if it were me (with masters hat off)I would find an ASC unit at FAB or somewhere similar,ensuring part numbers match(part numbers do have a habbit of superseeding to different numbers-if unsure of unit buying take part number and ring BMW dealer parts with your chassis number and p/n you have got to see if its right)Once you have it and fitted it you will need to take it to local BMW dealer and have the ASC encoded (1/2 hour)
The early E39's to about '99 had an issue with sporadic ASC intervention.Quite often this would leave NO fault codes in the memory.
As long as the tread depths are even ie 4mm all round not 2mm rear 6mm front,and it is proven the wheel speed sensors and reluctor wheels(sensor pick up) are good and so on then the Control unit is the way forward-but thats as long as it has been fully diagnosed.I cant say for definate as I havent seen it.
The control unit is easy to fit.....4 torx 20 screws,no bleeding or removal of actual hydraulic unit needed.You must ensure the area is clean first-ie no mud.
In an ideal world you should,to ensure a long term fix buy the new unit and then encode it with the BMW SSS system.
But if it were me (with masters hat off)I would find an ASC unit at FAB or somewhere similar,ensuring part numbers match(part numbers do have a habbit of superseeding to different numbers-if unsure of unit buying take part number and ring BMW dealer parts with your chassis number and p/n you have got to see if its right)Once you have it and fitted it you will need to take it to local BMW dealer and have the ASC encoded (1/2 hour)
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