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Old 28th July 2015, 15:48   #1
daznkel
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Default ABS Live Data?????

I think I already know the answer, but here goes!

Is there anything that can read ABS live data to enable me to diagnose which sensor cable or reluctor ring is faulty on my car please. My mates snap on gear at the garage cant read it. I am guessing T4 only?
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Old 28th July 2015, 17:03   #2
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Hi

This told me what I already knew about an ABS sensor - not cheap cheap but a sort of halfway T4.

http://pscan.eu/features/abs57.html

If there is a fault code it will show it.

I suppose it depends how much use you make of it as opposed to T4 session from one near you.

Would assist you if you were a bit closer.
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Old 28th July 2015, 17:20   #3
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Make up a "jump lead" to connect the rear sensors one at a time to the drivers side front.

When you plug in a duff sensor, your speedo won't work

So off to the scrapyard armed with a pair of snips and nab the blue connector and the plug from an abs sensor and get soldering

Brian
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Old 28th July 2015, 17:24   #4
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Quote:
Originally Posted by daznkel View Post
I think I already know the answer, but here goes!

Is there anything that can read ABS live data to enable me to diagnose which sensor cable or reluctor ring is faulty on my car please. My mates snap on gear at the garage cant read it. I am guessing T4 only?
Interested to know what Snap-On scanner your mate has.

I have a Solus Pro & Modis Ultra, both read the ABS etc on the R75 & ZT fine.

As a starter, if your speedo has stopped working, the problem's with the O/S front (you may also see the fuel gauge reading incorrectly).
If you have cruise control & that's stopped working, the problem's with the N/S front.

If neither of the above apply, the problem's more than likely on the rear.

The R75 & ZT/ZT-T doesn't have a reluctor ring for the ABS, the wheel bearing has a magnetic pickup buit into it.

A good tip by marinabrian above for testing without a scanner.

Last edited by mh007; 28th July 2015 at 17:26..
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Old 28th July 2015, 17:31   #5
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Quote:
Originally Posted by first-things-first View Post
Hi

This told me what I already knew about an ABS sensor - not cheap cheap but a sort of halfway T4.

http://pscan.eu/features/abs57.html

If there is a fault code it will show it.

I suppose it depends how much use you make of it as opposed to T4 session from one near you.

Would assist you if you were a bit closer.
No problem. Thanks for the heads up!

Quote:
Originally Posted by marinabrian View Post
Make up a "jump lead" to connect the rear sensors one at a time to the drivers side front.

When you plug in a duff sensor, your speedo won't work

So off to the scrapyard armed with a pair of snips and nab the blue connector and the plug from an abs sensor and get soldering

Brian
I just so happen to have 2 cables with the blue connector on from 2 old hubs! So I will knock something up tomorrow.

Thanks for you help Brian. What a fountain of knowledge you are!
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Old 28th July 2015, 17:44   #6
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Originally Posted by mh007 View Post
Interested to know what Snap-On scanner your mate has.

I have a Solus Pro & Modis Ultra, both read the ABS etc on the R75 & ZT fine.
I will ask him tomorrow which scanner it is. The speedo is working, so not OSF and I don't have cruise. I will make up a cable and go from there. Thanks!
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Old 28th July 2015, 19:06   #7
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Quote:
Originally Posted by daznkel View Post
I think I already know the answer, but here goes!

Is there anything that can read ABS live data to enable me to diagnose which sensor cable or reluctor ring is faulty on my car please. My mates snap on gear at the garage cant read it. I am guessing T4 only?
What are your symptoms daznkel? I knocked up an extended lead so any sensor could be plugged into the OSF using the speedometer readout as a diagnostic a few years ago.

Works well with a duff sensor or damaged magnetic reluctor, but if the reluctor ring is only slightly damaged, or the air gap a tad too big between sensor and reluctor the reading is good at speed and only fails when the wheel is rotating very slowly, so doesn't show up on the speedometer.

If that is your problem then measure the voltage at the sensor as you slowly rotate the jacked up wheel - it should change between 0.7V and 1.7V as each segment is passed. Chalk the wheel when you don't get the correct voltage, and if it is in the same place every revolution then likely a reluctor problem.

On the rear wheels check for corrosion on the backplate - it can wear the magnetic reluctors away on the bearings.

This is a front hub being checked prior to fitting on the car. The chocblock in the extended cable saves pinning through the insulation of the sensor cable.

[IMG][/IMG]

Last edited by Mike Noc; 28th July 2015 at 20:10..
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Old 28th July 2015, 19:26   #8
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Diagnosing Antilock Brake System Wheel Speed Sensors

Copyright AA1Car

When a wheel speed sensor (WSS) fails or there's a problem in the sensor's wiring circuit, it usually disables the ABS system and causes the ABS warning light to come on. Loss of a wheel speed signal is a serious problem because the ABS module needs accurate input from all its sensors to determine whether or not a wheel is locking up. Without this vital information, the ABS system can't do its thing.
Wheel speed sensors produce an alternating current (AC) output voltage that varies in frequency and amplitude with wheel speed. The faster the wheel turns, the greater the frequency and amplitude of the sensor's output signal. The strength of the signal can be affected by resistance in the sensor, resistance in the wiring and connectors, metallic debris on the end of the sensor, and the air gap between the sensor and tone ring mounted on the axle, hub, brake rotor, drum or CV joint.
A narrow air gap is usually necessary to induce a strong signal in the sensor's magnetic windings. Air gaps typically range from .016 in. to as much as .050 in. (0.40 to 1.3 mm) depending on the application. If the ABS warning light is on and you find a code for a wheel speed sensor (and the sensor is adjustable), the problem may be nothing more than too wide an air gap. Use a brass or nonmagnetic feeler gauge set the gap to the factory recommended specs.
Variations in the air gap can also cause fluctuations in the sensor's output signal. These may be caused by bad wheel bearings or missing, broken or chipped teeth on a tone ring. Even minor damage to the tone ring that's nearly impossible to see can sometimes cause a problem. One equipment supplier makes a test bench with a magnetic pickup and oscilloscope to check tone rings on remanufactured FWD axle shafts. The setup simulates the signal produced in a wheel speed sensor. Tests have shown that a variation in height of only about .010 inch on a single tooth can cause a noticeable fluctuation in the sensor's output signal!
WHEEL SPEED SENSOR CHECKS
One way to check a suspicious wheel speed sensor is to measure its output voltage. One way to do this is to plug a breakout box into the ABS module's wiring harness and attach the test leads from a digital volt ohm meter (DVOM) to the appropriate pins for the WSS circuit.
A good wheel speed sensor will generally produce an alternating current (AC) voltage reading of 50 to 700 MV when the wheel is spun by hand at about one revolution per second. Refer to a shop manual for the sensor's exact voltage specifications.
A low voltage reading or no reading calls for a direct measurement of the resistance in the WSS circuit (with the key off). This should be done through the breakout box to check the entire circuit. A good wheel speed sensor and circuit will typically have a resistance of 800 to 1400 ohms (specs vary, so refer to a manual for the exact numbers).
If the sensor circuit has too much resistance, reads open or is shorted (little or no resistance), measure the resistance across the sensor itself. If the sensor itself reads within specs, the problem is in the wiring or connectors. If not, then you have identified a bad sensor that needs to be replaced.
SCOPE CHECKS
This isn't something a do-it-yourselfer can do, but a dynamic check of a sensor's output with an oscilloscope is one of the best ways to analyze the performance of a wheel speed sensor. The waveform on the scope can reveal problems that might not be detectable by other means. A damaged tooth on a tone ring, for example, may not produce a noticeable change in the sensor's output voltage if you are reading the output with a DVOM or an analog voltmeter. But it may distort the waveform enough to upset the operation of the ABS system and set a fault code.
The scope connection can either be made through the breakout box or hooked directly to the wheel speed sensor. A "good" scope pattern should show a sine wave alternating current pattern that changes both in frequency and amplitude with wheel speed. Spinning the wheel faster should cause both frequency and amplitude to increase.
If the scope pattern is flattened (diminished amplitude) or is erratic, it usually indicates a weak signal caused by an excessively wide air gap between the tip of the sensor and its ring, or a buildup of metallic debris on the end of the sensor. A weak signal can also be caused by internal resistance in the sensor or its wiring circuit, or loose or corroded wiring connectors.
Damaged or missing teeth on the sensor ring will show up as flat spots or gaps in the sine wave pattern. A bent axle or hub will produce an undulating pattern that changes as the strength of the sensor signal changes with every revolution.
Something else that can be detected with a scope is mismatched parts. If the brake rotor, CV joint or axle has been recently replaced, and the new part did not have the correct number of teeth on the sensor ring, it will cause the sensor to read fast or slow compared to the others and set a fault code. Comparing the sensor patterns side-to-side will reveal this kind of problem.
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Old 28th July 2015, 20:45   #9
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Quote:
Originally Posted by Mike Noc View Post
What are your symptoms daznkel?
When the car is fired up, the ABS self check is initiated and the light goes out, as per usual.
The car drives fine, no flickering of the ABS light. However, under braking (again no light) the pedal judders under foot as if the ABS is cutting in, accompanied by a grinding noise. Braking efficiency does not appear to be affected.
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Old 28th July 2015, 20:57   #10
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I had a similar, if not the same problem/symptoms with my 45, it turned out that the ABS rings were rusted.
The 75 has them built into the bearings, so not sure how it would be damaged without bring the light on ?

Craig.
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