ABS Problem MG ZT-T

[FrenchMike]

Congrats and thanks for updating
always good to know your trick

Mike

[SD1too]

Originally Posted by grteam

.... in 1 minute or so it started to move, so in 2 minutes it was out.

Well done Horia, not many of us manage to get it out in one piece. Thanks for the update.

Simon

[larryr123]

Hi Guys, After a very long break, I'm hoping to have another go at fixing my low speed ABS judder problem. Having checked everything last time, I wondered if anybody knows a definitive test mechanism that will determine how to find the cause of ABS judder when no warning light comes on.
I tried disconnecting each ABS plug, but they don't work independently so it's not possible to isolate the fault to any one wheel. Once one is disconnected, the whole ABS is locked out and the speedo deactivated -- rather silly really, at least the speedo should be independent of the ABS system.

Any clues? -- so far changed front right sensor twice, cleaned gaps on rear wheel, done multimeter space tests around the tyre on each wheel, changed front right hub, changed rear left hub, 4 new tyres, new brake discs on the front and new pads. Cltreaned the ABS controller plug under the battaery housing.

Still at a total loss how to fix this and garages seem even less able to do anything other than plug it into a tester that tells you nothing important.

I'd like to keep the old girl on the road, and am having air con re gassed tomorrow.

Any thoughts?
Larry

[Heddy]

Not trawlin' through all the posts but based on the last one....change the rear right hub.

[trikey]

Originally Posted by Heddy

Not trawlin' through all the posts but based on the last one....change the rear right hub.

That's where my money wold be too...

[larryr123]

Hi Guys, Thanks for the response.
Given that I've tried replacing so many components, I'm really looking for a definitive method of testing and determining where the fault lies.

Clearly there is no warning light, so I'm assuming the ABS controller and the sensors are all now functional -- or is that a wrong assumption?

If I disconnect the ABS the low speed judder goes, so it's definitely ABS related.
A T4 Tester is useless as it doesn't tell you anything about where the problem lies and the chalk and meter test on each of the 4 wheels is inconclusive.

I've so far :-
1. Changed front right sensor and fitted a new wheel bearing, this extinguished the warning light and returned the speedo again -- so I'm now assuming this wheel is OK.
2. Changed both rear hubs in 2014 and changed the rear nearside again this year. Also cleaned all rust off back plates.
3. Fitted new tyres all round, two new front discs and pads, and replaced a new rear coil spring.
4. Took out the battery component and checked the controller plug was dry, and cleaned all the individual pins before reconnecting.

The car still passed the MOT with the low speed judder, because there is no ABS warning light lit.

I'm stumped and would really like to give the car to someone who knows how to fix it. !!

Regards Larry

[HarryM1BYT]

Originally Posted by larryr123

and the chalk and meter test on each of the 4 wheels is inconclusive.

What do you mean by 'inconclusive'? Either the pulses appear at every point / chalk mark they should appear, or they miss sometimes. If any are missed, your ABS system will be triggered and cause exactly the judder you are experiencing.

Carry out the check very carefully, use something like a brick as an edge marker and something to mark the tyre at trigger points, then turn the wheel slowly, to ensure you see every single pulse show without fail. The spacing of the marks around the tyre should also be absolutely even.

Another scenario, is where the ABS controller might not be receiving the signals sometimes, due to a wiring issue or poor connection. It might be worth your unplugging and reconnecting the ABS controllers plug a few times, to clean those connections up.

[marinabrian]

Originally Posted by HarryM1BYT

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.

T4 will see it as a plausibility fault, and this will be logged in the ABS ECU Harry

Given where the OP is located, I would suggest he contact Phil-T4 in the first instance, and not bother wasting time swapping this that and the other to try and pinpoint the failure

Oh and Heddy is right, the magnetic reluctor is embedded in the bearing oil seal of the rear and front hubs, and corrosion build up can affect the magnetic flux thus interfering with the abs sensor pulse, very easily identifiable using ABS live data on T4

Brian

[larryr123]

""T4 will see it as a plausibility fault""

Not sure what a plausibility fault is, or whether that pinpoints it to the actual cause and on which wheel.
When the test was run last time no faults were shown, so I doubt there is a need for another T4 test.

Harry -- I did the chalk test three or 4 times and i honestly couldn't determine any gaps. It's not a very scientific measurement method though I assume.

There really should be a piece of test equipment that actually identifies erroneous signals and pinpoint where they are coming from. An oscilloscope perhaps, although I would have thought that would be built into the T4.

I've had the plugs in an out loads of times, so I doubt there is a connection problem, especially as I was getting a reading on the supply wire and the signal wire on all 4 wheels.

On the dirt and corrosion, I cleaned up the hubs and back plates.
Most people on here indicate that the faults usually occur on the rear wheels.
My original fault was the drivers front wheel, as the speedo failed and the ABS light came on -- but that has been rectified with a new sensor and a new front wheel bearing. Yes all the reluctor rings are embedded in the wheel bearings -- on the rears they reside in the slide on hubs and are much easier to change - the fronts a much more difficult.

Larry

[marinabrian]

Originally Posted by larryr123

""T4 will see it as a plausibility fault""

Not sure what a plausibility fault is, or whether that pinpoints it to the actual cause and on which wheel.
When the test was run last time no faults were shown, so I doubt there is a need for another T4 test.

Harry -- I did the chalk test three or 4 times and i honestly couldn't determine any gaps. It's not a very scientific measurement method though I assume.

There really should be a piece of test equipment that actually identifies erroneous signals and pinpoint where they are coming from. An oscilloscope perhaps, although I would have thought that would be built into the T4.

I've had the plugs in an out loads of times, so I doubt there is a connection problem, especially as I was getting a reading on the supply wire and the signal wire on all 4 wheels.

On the dirt and corrosion, I cleaned up the hubs and back plates.
Most people on here indicate that the faults usually occur on the rear wheels.
My original fault was the drivers front wheel, as the speedo failed and the ABS light came on -- but that has been rectified with a new sensor and a new front wheel bearing. Yes all the reluctor rings are embedded in the wheel bearings -- on the rears they reside in the slide on hubs and are much easier to change - the fronts a much more difficult.

Larry

Driving the car with the live data showing on T4 will certainly identify which wheel(s) are causing the issue.

You can't beat seeing the output speed from each wheel in real time, did Phil T4 your car, or someone else?

Brian