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Vauxhall Astra H 1.8 2008 - ABS light on - Fixed #

Posted by Malcolm Tripp on August 31, 2012, 6:43 pm

Year of Manufacture *: 2008
( Optional ) Engine Code or CC: 1.8 petrol

ABS light on, diagnosis points to o/s/f wheel
On driving vehicle at 30 kph that wheel on live data drops occasionally to between 8 and 14 kph momentarily.

Tried scoping sensor with Pico but weird trace suggests this is not a straightforward a/c waveform.

Anyone got any ideas of the operation ? only two wires, is it creating milliamps that you need a special low amps clamp to see.

The sensor and hub come complete so I would rather be certain before condemning it.

Re: astra H

Posted by Mark Carter <iframe src='https://members4.boardhost.com/ukautotalk/info/user=UKAT1428' width='330' height='300' border=0 style='border:none;'> on August 31, 2012, 8:23 pm, in reply to "astra H"
Mark Carter

>>> but weird trace suggests this is not a straightforward a/c waveform <<<
Probably an active sensor, try scoping it earth biased.

Mark

Modern cars, Its all wizardry and witchcraft

Re: astra H

Posted by Lee Mackintosh <iframe src='https://members4.boardhost.com/ukautotalk/info/user=UKAT1348' width='330' height='300' border=0 style='border:none;'> on September 1, 2012, 12:33 pm, in reply to "Re: astra H"
Lee Mackintosh

Can't remember the proper descripton but i'm sure you scope the supply and you'll see it switching on top of the 12 volts.

A square wave form on top of the 12v supply.

Something like that anyway. I think an very low amps clamp is better but voltage trace can be achieved.

If you ac coulple it you see more detail and can use a lower voltage scale.

Hope you understand what i'm trying to explain.

Fixed #

Posted by Malcolm Tripp on September 12, 2012, 8:20 pm, in reply to "Vauxhall Astra H 1.8 2008 - ABS light on #"
Message modified by board administrator September 13, 2012, 2:53 pm

Seems my Pico has a fault and has gone to Pico hospital, borrowed a friends and now have a clear picture of whats going on.

Blue trace is o/s/f wheel
Red trace is n/s/f wheel
Both earthed at battery
All images zoomed in.
Capture taken from ABS unit backprobed pins 5 & 9 whilst still plugged in

Running voltage observed with slight voltage increase just as Lee suggested, blue trace is dropping out for 20ms.

Hub replaced as one unit with confidence of a fix, old one had a considerable build up of rust between pickup ring and bearing.

Hope this post helps someone else

Re: Fixed #

Posted by James Eardley on September 12, 2012, 8:51 pm, in reply to "FIX"
Message modified by board administrator September 13, 2012, 2:54 pm

Hi Malcolm

If you apply scaling to your capture on the pico it will help to exaggerate the squarewave and spot a problem

hth
James

Re: Fixed #

Posted by malcolm tripp <iframe src='https://members4.boardhost.com/ukautotalk/info/user=UKAT5337' width='330' height='300' border=0 style='border:none;'> on September 13, 2012, 4:10 pm, in reply to "Re: Fixed #"
Malcolm Tripp

James

Not sure how to apply scaling but when I get it back I will check it out, thanks for the suggestion.

I had enough trouble getting the capture on this website due to Pico files not being acceptable, and having to change them to BMP not being a computer whizz !!!

Re: Fixed #

Posted by Lee mackintosh <iframe src='https://members4.boardhost.com/ukautotalk/info/user=UKAT1348' width='330' height='300' border=0 style='border:none;'> on September 13, 2012, 4:20 pm, in reply to "Re: Fixed #"
Lee Mackintosh

Not sure how you do it on Picoscope either but with my MODIS i just select AC Coupled which then allows you to use alot smaller voltage ranges.

This then enables much better signal capture and easier to spot glitch's in real time.

I did play around with a Fiesta and believe me it works far better.

Re: Fixed #

Posted by James Eardley <iframe src='https://members4.boardhost.com/ukautotalk/info/user=ukat3143' width='330' height='300' border=0 style='border:none;'> on September 13, 2012, 8:42 pm, in reply to "Re: Fixed #"
James Eardley

Hi Malcolm

This is me trying to use the First Look Sensor to try and measure the cooling system pressure against primary current to diagnose headgasket failure.

This is the original capture

This is the same capture with scaling applied to the blue channel.

This is the same capture with scaling minus/taken away (couldnt think of how to describe sorry)

BLUE= cooling system pressure
RED= cylinder 1 primary current

The scaling button is here, click and play.

NOTE,
I found this diagnostic approach does not work in trying to find out which cylinder it blowing it to the water system.

The results seem to depend on how close, the return pipe to the header tank, is to the water pump.

Although it does prove that the water pump is turning.

As for posting the pictures,
I find it easier to use waveform snips or screen print to change from psdata format.

hth

James

Re: Fixed #

Posted by Andrew West <iframe src='https://members4.boardhost.com/ukautotalk/info/user=UKAT5350' width='330' height='300' border=0 style='border:none;'> on September 13, 2012, 9:39 pm, in reply to "Re: Fixed #"

Sorry to everyone for taking this thread slightly off topic.
Hello James,
I have tried similar using the wps500 & intially did the same as you to try & identify a specific cylinder leak. I did find though that using the wps driving under load you could see a definite rise in coolant system pressure in line with engine load . This was on a TD5 landrover, which can be difficult to confirm a gasket leak on.
Regards, Andrew
ps Malcolm, it may be possible to see the abs sensor operation better by using a standard low amps clamp & getting several windings around the jaws, if the wire length allows.

Re: Fixed #

Posted by malcolm tripp <iframe src='https://members4.boardhost.com/ukautotalk/info/user=UKAT5337' width='330' height='300' border=0 style='border:none;'> on September 14, 2012, 4:18 pm, in reply to "Re: Fixed #"
Malcolm Tripp

I do use the scaling buttons but mostly to move the pattern up or down the page, will give it a go when I get Pico back, only been gone a few days and now realise how much we miss it !!!

Re: Fixed #

Posted by malcolm tripp <iframe src='https://members4.boardhost.com/ukautotalk/info/user=UKAT5337' width='330' height='300' border=0 style='border:none;'> on September 15, 2012, 10:19 am, in reply to "Re: Fixed #"
Malcolm Tripp

James

How did you capture the whole screen ?
I only seem to get the waveform with none of the settings !!!

Re: Fixed #

Hi Malcolm

The pictures I posted were taken using The Snipping Tool. It is a function that is on my lap top you can snip/take a picture of any part of the screen and it saves it in a folder ready to be posted.

I press the start button and select it from the sub-menu.

My last laptop didn't have the snipping tool it maybe something to do with Windows 7.

You could try using the Print Screen button on your PC, this will take a picture of the whole screen instead of being able to take a picture of just a section of the screen.
But you would see the settings.

hth
James

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