Quote:
Originally Posted by HarryM1BYT
Reading that, suggests you are misunderstanding how to carry out the test...
It is NOT just a matter of checking the voltages, but of marking the tyre where the voltage changes. A light coloured crayon, with a brick or similar as a fixed marker works well. That ensures that a full continuous set of changes of voltages/ pulses appear around the circumference of the wheel/tyre. You may need to repeat it several times to be sure the pulses appear without fail.
The judder happens when pulses signals fail to appear, when they are expected. Most likely they will be missed at lower speeds, hence the low speed judder you are experiencing.
T4 and other diagnostics will not see it as a fault, because it is doing more or less what it is supposed to be doing - generating mostly regular pulses.
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Thanks Harry -- I relied on the guys at the garage to run the test. I don't recall any chalk marking. This was the first time I'd witnessed this kind of test, so wasn't aware of the full procedure, despite having read up the basics of how the ABS system works.
I have a low cost cable, and engine test software, but nothing that tests the ABS. I've run the test at the garage twice so far, so will avoid that since I doubt the guys understand what the effect of placing chalk marks on the tyres will do. They did rotate each wheel individually by hand, as well as trying a drive test with the test rig plugged in and monitoring the readings.
The only real way to measure this I suppose would be on an oscilloscope and look at the uniformity of signal sent back to the ABS control unit.
I'll have a go at a new hub swap, as I think the absence of a scope I'm not going to get anywhere -- and it's cheaper than another inconclusive ABS test.
I did notice on the rear nearside hub, that a lot of the green gel had leaked, so I cleaned it up before reinstalling it - perhaps this was a factor in the reluctor ring deteriorating. It still puzzles me why one has a visible brass perforated ring on the outside and the other doesn't.
Regards Larry -- I'd happily do without the ABS (it's a bit of a pain), as I don't drive like a lunatic and don't use the car to commute -- I won't be selling though as I've had this since new, even if I get another car.