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944 S2 - ABS not working

jmelhuish

jmelhuish

PCGB Member
Member
Hi All,
Over the weekend I changed the front brake pads on my S2. To bed them in I took the car out for a drive at the local industrial estate and then did some emergancy stops as I'd never had to stop the car in this way before. I found that the ABS doesnt work so I checked the fuse which was fine. Before I start where else should I start looking to fault find this problem?
Thanks
Jason
 
I dont know about on a 944 specifically but filthy or cracked or rotten reluctor rings are always a good start.

I take it you havnt disturbed the abs wire/connector i.e was it deffo working as by your wording I assume you are unsure ?



Mas
 
Im not sure it worked in the first place. Im going to start looking next week. Thanks for the info.
 
I suggest you download a workshop manual off the internet - there is a whole section on troubleshooting ABS brakes in there. Several places have free ones (as I found out after I paid for one) - Cannel is one IIRC.

These things aren't the easiest to use in electronic form but at least it gives you a good idea of whats involved.
 
At the risk of being boring... The ABS system on the 944's is pretty basic:

  • ECU
  • Pump
  • 4 Wheel Sensors
  • Wiring and relays connecting them together, including warning light on the dashboard
Stating the obvious, when the system stops working one or more of the four sets of components has broken/ become disconnected.

From listening to a number ABS related issues other people have had where the system isn't working but the warning light comes on just above walking speed, this appears to be either a duff wheel sensor or earth connection .

If as you describe the system isn't working and you've no light on, I would suggest one of two things:

a. Previous owner knew this and removed the ABS lightbulb from the dashboard to hide this at MOT/sale time (not unheard of....)

b. The Pump and/or ECU have failed and aren't even providing a failure signal to the dashboard - this happened on my Turbo ~ 6yrs ago and had to replace both. Pump seized then fried the ECU in the process.

Let us know how you progress !

Chris

 
Given that you don't know if it ever worked I would say that it's the ECU. My ABS light came on a while ago and this means that the ECU has checked the system and found a fault. If the system isn't being checked it won't tell you so my guess is that the ECU has never worked. Does it come on when you start to ignition or when you're moving?

Buy a second hand one from e-bay (about £50) and swap it for yours. It's an easy swap (right hand side of the drivers foot well, just underneath the dash). You'll need to unscrew the bracket holding the connector and disconnect it.

Second guess is that it's the wiring on the sensor that you disturbed so double check this.

I doubt it's the pump. You should be able to hear the pump start if you pull of, it is primed at 10mph.
 
If it's being controlled then the pump should self test at above 6mph. It sounds like a coffee grinder for about a second coming from near the offside front wheel.

No sound? Then its the controller or the pump.
 
My S2 ABS doesnt work either... I went for the 'easy' option and bought another ECU but no joy :( - I havent made any more progress yet.

From my reasearch you can narrow the search down by observing the abs light on the dash (if it hasnt been removed like mine was). If it has, just swap one of the other bulbs over to it temporarily.

Ok from what i remember,

If the light is on after you start the car, but before you move, the fault is ECU/relay/earth
If the light doesnt come on till you start moving (6mph) its one of the wheel sensors. - You might be able to find out which one by jacking the car up, and spinning each wheel individually until the light comes on.
If you know the ABS bulb works, but never lights up, yet the ABS still doesnt work, it means the ABS pump is toast.
 
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