Hi,
Can anyone tell me exactly what the difference is between ABS units with green and purple stickers. I am aware that one is pre 09/89? (green) and purple stickered units are after this date and that units must match green/purpled stickered devices in the system.
My car had a purple stickered unit in it and the ABS light was suddenly comming on when self checking before startup some time ago. I checked everything and couldnt find a problem, on replacing the ABS unit with another purpled stickered unit the fault was still flagged. I tried another one and I got the same problem, I replaced the unit with a green stickered unit and the light flashes as normal in the self check and goes off after self check as it did before normally when it was working.
After a year or so I am not convinced that the ABS is working properly as I have never felt the distinctive vibrations through the pedal which was occasionally felt when braking in the wet etc. I know the ABS system appears to working in some way as I have still get the usual ABS light comming on when there has been a problem with the sensors, connectors etc and when driving at high speed with excessive road vibration (dodgy cable repair to a sensor).
Any idea of what the difference may be?. I am starting to suspect I have some earth problems with the car as I am seeing voltage drops/lights dim when operating certain electrics and my FM radio reception is not too hot now. I was thinking of getting hold of another purple stickered ABS unit and trying to diagnose the fault further.
regards
John
BX ABS units
Well, from a personal point i have never heard of an ABS unit failing, ever. Strange goings on as a result of poor grounding or supply to the ECU and the usual failed sensors, but never the actual 'pump' failing.
Given that the sensors them selves are reluctance based i suspect that poor voltage potential (low battery, poor earth) could cause fluctuations in the coils resulting in the ABS kicking in. Or even just a poor supply resulting the ABS failure.
Testing the ABS is actually working should be relatively simple, find a quite/disused dust or gravly road with an even surface, get upto 20mph+ and stand on the breaks. The resultant marks on the road surface should make it clear if the wheels are releasing during the skid. You could even try a covered stretch of concrete in a factory or warehouse for example.
I could probably get a pump as far as coventry if that helps, i might have one in the garage but suspect i might have to get one from storage.
Given that the sensors them selves are reluctance based i suspect that poor voltage potential (low battery, poor earth) could cause fluctuations in the coils resulting in the ABS kicking in. Or even just a poor supply resulting the ABS failure.
Testing the ABS is actually working should be relatively simple, find a quite/disused dust or gravly road with an even surface, get upto 20mph+ and stand on the breaks. The resultant marks on the road surface should make it clear if the wheels are releasing during the skid. You could even try a covered stretch of concrete in a factory or warehouse for example.
I could probably get a pump as far as coventry if that helps, i might have one in the garage but suspect i might have to get one from storage.
Hi Vanny,
Thanks for your reply, I did go through the full ABS fault finding document and tested all the suggested points, rather nice document, I would love to get hold of the rest of these diagnostics. All measurements did seem ok, I wonder what the difference is between purple/green boxes. There must be a hardware/software difference if the acutal pump must also match the ABS ECU.
Could well be an earth problem as I am starting to see some problems with radio reception (FM has terrible reception), replaced the antenna, cable, connector and several earths but no joy so far.... may be the head unit that gone. Also dimming dash lights when the sunroof is operated.
I have tried to stamp on the brakes a few times but dont feel the vibrations through the pedal or hear the usual tapping from the pump, I guess I will only know for sure if we get some snow.
Are you based in Coventry?, I may still have my old ABS ECU somewhere. If not I should be able to get another second hand one from a garage I used quite a bit over the years in birmingham once I find out where they have moved to. Is the pump easy to change?, I am always paranoid about getting air into the system and also breaking bleed valves so usually get the garage to do this.
Seems that the ABS is the least of my problems at the mo... another post coming on!.
regards
John
Ps. Think I spoke to you many years back and joined, I was then based in scotland... still got the same BX
Thanks for your reply, I did go through the full ABS fault finding document and tested all the suggested points, rather nice document, I would love to get hold of the rest of these diagnostics. All measurements did seem ok, I wonder what the difference is between purple/green boxes. There must be a hardware/software difference if the acutal pump must also match the ABS ECU.
Could well be an earth problem as I am starting to see some problems with radio reception (FM has terrible reception), replaced the antenna, cable, connector and several earths but no joy so far.... may be the head unit that gone. Also dimming dash lights when the sunroof is operated.
I have tried to stamp on the brakes a few times but dont feel the vibrations through the pedal or hear the usual tapping from the pump, I guess I will only know for sure if we get some snow.
Are you based in Coventry?, I may still have my old ABS ECU somewhere. If not I should be able to get another second hand one from a garage I used quite a bit over the years in birmingham once I find out where they have moved to. Is the pump easy to change?, I am always paranoid about getting air into the system and also breaking bleed valves so usually get the garage to do this.
Seems that the ABS is the least of my problems at the mo... another post coming on!.
regards
John
Ps. Think I spoke to you many years back and joined, I was then based in scotland... still got the same BX
More than likely, been at this game for too long now!Ps. Think I spoke to you many years back and joined, I was then based in scotland... still got the same BX
Swapping the ABS pump is a doddle, i use a 'regular' brake pipe spanner to undo the unions (8mm IIRC) with a spanner on the in line union just behind the battery. Make usre the pipes go back in the right order though i can't see how you might get it wrong. My understanding is that the whole hydraulic system is self bleeding including the pump.
Are both types of ECU made by ATE? I wonder if there was a different supplied at some point.
I am based in Cov, but still have a lot of spares and parts in Liverpool.