Vauxhall Owners Network Forum banner

1 - 20 of 23 Posts

·
Registered
Joined
·
195 Posts
Discussion Starter #1
Hi Folks, the dreaded ABS dashboard light came on yesterday. Today I found the front offside sensor had a very high resistance so I removed it. This took 4 hours as was rusted in and meant smashing it to get it all out in bits. I then found a replacement almost unobtainable apart from one site asking £150 for one. I have ordered a used Cavalier one which looks similar but on a shorter lead for £12.50 which I am hoping I will be able to splice a longer lead on. The question is in case this doesn't work does anyone know of a compatible part that's more available.
 

·
93 Carlton 2.0 Diamond Estate, 06 Vivaro 1.9 CDTi
Joined
·
1,104 Posts
Hi, I have some experience of the ABS sensors on my Carlton.
Firstly, are yours the plastic or stainless steel type, the plastic ones are less hassle as they don't short to earth when corroded, always fit with a good coating of copper slip to stop any corrosion.
Secondly, you can lengthen/shorten the leads but solder the joints & cover with shrink sleeving on both joins & then on both wires, then cover the join with self amalgamating tape a good distance past the join.
Thirdly, you can get most vauxhall ABS sensors to fit if they are the same size, the differences are mainly in the orientation of the fixing hole/s in relation to the sensor pick up ( the sensors are length ways across the activating ring ) there are also some differences in the orientation of the wire but most can be overcome with a slight reroute of the cable with safety in mind.
I have actually front sensors fitted to the rear on my car with a slight mod to the fixing as the fixing holes are 90 Deg's out.
I have just purchased some new Cavalier rears as they are the same except for the length of cable as a spare set just in case.
 

·
Registered
Joined
·
195 Posts
Discussion Starter #3
Thanks for reply that all sounds hopeful. I guess the original must have been the stainless steel outer though it was so corroded it came out in bits not much bigger than a pinhead, I thought it was just steel. A great pity the manufactures don't use copper slip. As well as the cavalier sensor I ordered a Vectra sensor, the lead length is perfect, it is plastic so I am hoping will fit. The cavalier sensor hasn't arrived yet. If I do need to use it and extend the lead I will solder and heat shrink.
I had several Carltons they are great cars, the Omega suspension etc. is very similar and I am hoping the Vectra is similar again as it gives us a chance to obtain parts.
The sensors for the rear on the Omega seem more available and much cheaper, I think it might be difficult to use them on the front because they protrude too much. But as you have done it might be worth me getting them for spares for the rear.
 

·
Worn Out Member
Joined
·
5,494 Posts
Think about using something like cera tec rather than copper slip on these sort of components,
i'd been using copper slip for 40 + years and swore by it but changed to cera tec about 5 years ago,(although i still use copperslip when i can't find the ceratec):whistle:
it helps stop the galvanic corrosion you get when two dissimilar metals are in contact and i find brake parts definitely come apart a lot easier a few years down the line (y)
 

·
Registered
Joined
·
195 Posts
Discussion Starter #5
Hi Folks, the Vectra sensor cleared the ABS light until the vehicle moved when it returned, the cavalier sensor was similar but I only got the ABS light to clear once and on vehicle movement it came on again. Had a quick diagnostic done which confirms I am working in the right area. I have two problems, 1) My code reader wont read or reset ABS so I need to splash out any recommendations? 2) I don't know where K59 the ABS computer is located so I cant check readings at the other end of wiring loom does any one know where it is located? My next move is to pay the high price for the right sensor, which will still be a copy as original part is obsolete. I would add that I cleaned and checked the cog tooth wheel that the sensor works from, it looks in good order with no cracks etc. Don't you just long for the good old days when a decent driver could be trusted to do cadence braking to deal with locked wheels instead of a stupid computer with a reliability that fits with the 10p components it is made from.
 

·
93 Carlton 2.0 Diamond Estate, 06 Vivaro 1.9 CDTi
Joined
·
1,104 Posts
Do you have a multi-meter? if not get one!
You need to check the resistance on each of the sensors, and as you have metal ones you also have to check the resistance to earth. ( if one was crushed with rust, it's likely one of the others will be shorting to earth as well)
It seems pointless checking all of them at first, but you have to focus on the problem, be sure that any faults you find are the only faults and after fitting new parts and seemingly still getting the same fault, you haven't got a problem with another sensor that's causing it, or you'll be going round and round and not proving that what you think is OK is actually OK.
You also need to have the correct distance from the abs ring to the sensor, if the sensors you fitted are slightly shorter they may not work, did you check that the sensor pick ups are orientated the same way (both obvious, I know, but just checking!)
 

·
Premium Member
Joined
·
574 Posts
Pretty much all the advice given so far is spot on.


I’ve never owned an Omega as I’m still running a Carlton as a day to day car and haven’t yet progressed to the Omega, so as with others advice, I’ll be speaking from a Carlton perspective. It’s strange how at one time there would be a dozen Omega owners all giving advice on this, but now it seems to be just several Carlton owners that are left on here.


One thing I would add is to make sure you disconnect the negative side of the battery before working on the system – guess how I know this is a good idea!


It’s possible that you may have more than one faulty sensor.


As has been said, make sure the orientation is correct on the one you’ve fitted, as front to back are 90 degrees out from each other. The distance from the pole piece isn’t critical other than it MUST be close(ish) but not touching. If you’ve joined the wires to extend them, make sure you have kept the same polarity – yes, I know it’s alternating (AC), but there may be a phasing issue if you get it wrong, remember, the plugs are non-reversible for a reason.


You need to measure the resistance of all four sensors with a DVM. They tend to be anywhere from roughly 1 to 1.5K ohms and I’ve found they can be mixed and matched quite happily. I find the usual fault is an open circuit sensor, but I have had them with a shorted turn, which means that they may well give an in spec resistance reading, but will have virtually no output.


If measuring all the resistances of the sensors shows up nothing, then you’ll have to check them all individually for output. Jack the car up and pop it on stands so that all four wheels are hanging. With your DVM connected to each sensor in turn, give the appropriate wheel a good spin by hand and note the AC reading on your meter – it should be several volts depending on how fast you can spin the wheel against possible brake pad drag on the discs etc. While DVM probes can be persuaded to fit into the socket connector on the end of the sensor, it’s much better to make all the tests from the ABS ECU plug / socket inside the car. Make up some long test leads that will fit in the appropriate sockets on the ABS unit plug (once disconnected from the unit) without stressing the actual socket connectors themselves – I use a couple of small stiff pieces of wire pushed into the particular sockets and clip onto them with small insulated crock clips (your workshop manual will show a diagram indicating which sockets connect to which sensor). The leads should be long enough so that the meter can be close enough to read at any of the four wheels while being spun. Doing it this way saves a lot of grovelling under the car, and also tests the complete wiring right back to the ABS unit. I’ve had an instance where a sensor read absolutely perfectly on an ohms test, but had virtually no output, so was likely to have had a shorted turn in its very fine windings that was killing the output to a level that was too low for the ECU to pick up. If you struggle to turn a wheel by hand, put a wheel brace on one of the nuts and get it going that way.


On the Carlton the rear sensors are on cast brackets, so I just unbolt the bracket from the diff and swap the whole unit with one from my stock of dismantled spares. The front ones are more of a performance and have to be drilled, chiseled and dug out and then replaced with one that I’ve spent several hours gently persuading from an old complete front hub unit in the work bench vice. You can of course just swap the complete hub over, but then you end up messing up the camber. Next time I have a front one fail and I can’t be bothered with a lot of hassle removing one from an old hub, I might be tempted to just bung a complete front strut on – job done!


Last time I checked the price of new sensors at the Vauxhall main dealer must be at least 15 or more years ago, and I seem to think they were something like £87 plus VAT even back then. I bet they’re not available anymore now, so lucky I’ve got spares from old cars. I’ve still got four complete cars plus the parts from several others, so hopefully it’ll be a while longer before I finally have to give up on them and move onto an Omega – that’s if there’s still any of those left around, although a mate of mine bought a trade in one recently from a local dealer, which surprised me, as I hadn’t seen one on the road round here for years.
 

·
Registered
Joined
·
195 Posts
Discussion Starter #8
Hi Folks, thanks for taking the time with all the tips. Yes I have a Digital voltmeter, the nearside front sensor was about 1.6K and produced about 0.4Volt AC when wheel was spun, offside front was 2Meg Ohms ie open circuit, oddly when wheel was spun it produced similar voltage to nearside wheel. Which I would have thought impossible. Removing that sensor took four hours it came out in tiny bits so I have no idea how long it was. The Vectra replacement, the proximity of sensor to tooth wheel is very close around 1mm. It is 1.6K Ohm but when the wheel is spun only produces about 0.2 V Ac. the cavalier sensor and I didn't need to extend lead just re route it produced much the same. I removed the brake caliper and disc and cleaned and checked toothed wheel for cracks etc. Also proximity of sensor to teeth. Assembled no change. I am wondering if sensors from ebay are faulty as they cant be mounted any closer to toothed wheel.

With the facelift model a Haines Manual was not produced although I have the manual for the earlier model which helps. Good idea to check from the plug on the modulator, I would like to check from the ABS computer but I have no idea where it is. Does anyone know?

The check done by the garage with an ABS code reader and reset function with the Vectra sensor in place was as follows, he cleared the light, switched ignition off then on again, light still off which seems to indicate we have volts from the computer to check sensor, sensor resistance is OK so light stays off, vehicle moves off light comes on indicating not enough volts being produced by sensor. So I have sent off for another sensor. I haven't checked I have volts from the computer to the sensor although the garage test suggests that is Ok but I will if the new sensor also doesn't work, if that turns out to be the problem I will definitely need to find where the ABS computer is.
 

·
93 Carlton 2.0 Diamond Estate, 06 Vivaro 1.9 CDTi
Joined
·
1,104 Posts
Have you checked that the sensor orientation is correct, if incorrect it would give this fault, it's strange you have the same fault on both new sensors.
The pick up sensor should be horizontal in alignment with the teeth (if that makes sense?)
 

·
Premium Member
Joined
·
574 Posts
Start engine light goes out but comes on again when you move off indicates a duff sensor.

You misunderstand - you don't check the sensors from anywhere on the modulator, but on the plug to the actual ABS ECU, therefore you MUST find out where it is. On the Carlton it's under the front passenger seat.

0.2 and 0.4 volts is no good and indicates duff sensors, as said, it needs to be several volts, ie, anywhere from 2.5 to 5 volts is what I usually obtain when giving the wheel a spin by hand.

You mustn't have voltage going to the sensors - the sensors produce a constant AC voltage when the wheel is turning and this voltage is applied to and monitored by the ABS ECU.

I'm afraid to say that if you or anyone else has been applying voltages (other than from testing on the ohms range of a DVM), then the sensors may have been damaged. I once blew three out of four sensors all in one go by messing about with the system on a Carlton while the battery was still connected, that's why I warned of this in my previous post. You would think that with an ohms law calculation of the resistance of the sensor and only 12 volts available at the battery, that any current passing through a sensor would be so small as to not do any damage, but trust me, it can!
 

·
Premium Member
Joined
·
574 Posts
I've just had another thought - even if you've got the extended wiring polarity correct (that's if you had to extend the wiring on the sensor you obtained), it's possible that even though you've got the pole piece of the sensor correctly orientated to the teeth of the wheel, there's a possibility that you could have it a full 180 degrees out. The pole piece is connected to a permanent magnet within the centre of the sensor, and if it's 180 degrees out, then it will be generating a waveform which is out of phase to all the other sensors. All this wouldn't happen if the correct original type sensor were used. This still doesn't account for the low voltage obtained from two sensors, unless you're just not spinning the wheel fast enough, or perhaps not reading the meter correctly and it's 2.0 and 4.0 volts.
 

·
Premium Member
Joined
·
574 Posts
Just to add a bit more - I think I misunderstood a part of your previous post regarding applying voltage to the sensors. What you were saying regarding the ECU applying a small test voltage to the four sensors when the ignition is first turned on as a check, is correct.

I think you're going to have to spend a bit of time on this car and do some more tests such as finding the ABS ECU and running tests on the two rear sensors as a comparison - you won't want to do this from under the car as you'll have to get right underneath and release the connectors from their chassis connections and get covered in filth and muck in the process.

It's going to be very interesting for all of us readers if you manage to get an incorrect sensor to work on your car, but from your point of view it would probably have been better in hindsight to have just splashed out on the correct sensor in the first place. I will admit however, that if it were me, then I would have likely done the same as you to start with, as I'm a tight git!
 

·
Premium Member
Joined
·
574 Posts
Yet another thought - you mention that a sensor reading 1.6K is giving a low voltage the same as the open circuit sensor, well it's not completely o/c if you're getting a reading of 2Meg. If your readings are correct, then this indicates that you have two duff sensors. If you re-read my first post on this thread carefully, you'll see that I explain how a sensor with a single shorted turn will give a correct 'ohms' reading, but will give virtually no output - I guess you missed that bit? But give those wheels a really good spin and re-check your voltages before condemning that other sensor.
 

·
Registered
Joined
·
195 Posts
Discussion Starter #14 (Edited)
Folks this post has got out of order and is really replying to discussion on previous page, so I am up to speed now so bear with the duplication but I think we are all agreed.
Thanks also for the comments on the other page re copper slip, obviously not a good idea to get copper on rotor and I wasn't up to speed with the new stuff recommended.

Hi, again thanks for comments, yes I misunderstood when I thought you were testing from modulator, I realised my mistake when I looked at wiring diagram seeing that sensors are wired to computer. No one has injected any voltages into sensors, because the sensor I removed had to be smashed out I saw the wiring /winding inside sensor, it is finer than hairs on head so could easily be burnt out. However I think you will find the computer checks the sensor with car stationary by injecting a small voltage to it. There is also a youtube thing somewhere where they check the voltage coming down from computer to sensor plug but like yourself I was unhappy hooking up to this with ignition on.
Re the orientation of sensor, on the front sensor there is a locating screw on the top cover of sensor so it can only be fixed in one position ie cannot rotate sensor. I will look under passenger seat there are a lot of similarities between Carlton and Omega, very similar platform. I will get to the bottom of this problem, many thanks for your time. This post has got out of sequence to the two posts above it somehow so we are all saying the same thing twice. You are right about me being tight and the temptation to solve the problem spending £12 instead of £150 was too much . However I suspect I have been buying duff sensors from ebay.
 

·
Premium Member
Joined
·
574 Posts
I don't think it's so much that the posts have got out of order, as much as it's that I kept re-reading your post and thinking of other possibilities and making yet more posts with my thoughts.

I think you've just hit the mail on the head with you saying that you've used the original locating screw hole to locate the replacement sensor. You can't use the original screw hole if you're using a sensor that is intended to fit on the rear, as the sensor pole piece will be 90 degrees out from the teeth on the wheel. This is what the other poster and myself have been trying to say and is why you need to confirm that you have the pole piece (or pickup) of the sensor lined in the same orientation as the teeth on the toothed wheel, otherwise it won't work. Normally if you try to use a rear sensor on the front, you'd either have to drill and tap a new screw/bolt hole in the hub casting, or jam it in without the screw. Have a close look at the rear sensors on your car to see what we mean, as it's easier to see the relationship with the teeth on the rear, you can also get a better idea of the sort of gap you need, too.

Fake and dud components being sold on ebay is a huge problem. My mate bought 2 engine sensors from ebay and still had the same starting and running problems. I told him to meter the sensors and they checked out as regards to their DC resistance, but it wasn't until he splashed out and bought the genuine part that the running problems were solved instantly.

I've been thinking, and I've changed my mind regarding the self check when the ignition is first switched on and the engine started. I've never actually monitored with a meter or scope what's actually happening, but I don't think it actually sends any check voltage to the sensors, it's just not that sophisticated a system. I suspect that all it is is a bulb check so that it confirms that the dashboard lamp and its wiring are in working order. It could work by a capacitor being charged via a resistor of a given value which biases off a switching transistor after a few seconds within the ECU, although I've never actually studied the circuit to confirm what really does happen, someone else may be able to confirm if this is the case on these early systems. If it sent a test voltage to the sensors then it would be able to identify an open circuit one, which it doesn't.

I still think that the sensor that read 1.6K on your meter, but didn't show much output could also be faulty. If it were me I would be checking all four of them for output, both front and back. I've never been beaten by a Carlton ABS system - yet!

I think the Omega is a very similar car to the Carlton and is basically a Carlton with the corners rounded off. I think your pre-face workshop manual stands a good chance of covering the ABS system used on your facelift car.
 

·
93 Carlton 2.0 Diamond Estate, 06 Vivaro 1.9 CDTi
Joined
·
1,104 Posts
Re the orientation of sensor, on the front sensor there is a locating screw on the top cover of sensor so it can only be fixed in one position ie cannot rotate sensor.
I have done a quick drawing to explain the orientation, which is so important.
Sorry to go on about this, but as @HMK is also trying to explain, you have to start with the basics first.
 

Attachments

·
Registered
Joined
·
195 Posts
Discussion Starter #17
Hi and thanks again, I think I know how this misunderstanding has come about because I probably did say that Omega rear sensors were available but the front were much more difficult to obtain, however the Vectra and Cavalier sensors I have been trying to use come from the Front, they are not rear sensors. So their orientation should be OK. I was tempted to order rear sensors in which case and it may yet come to that so what you say could become relevant. I decided to bite the bullet and order the expensive correct sensors. I wont at this stage say which supplier but they returned my money and said they were out of stock, when I pointed out they were still advertising them but at an increased price they claimed confusion, I paid the new increased price and so far they do not appear to have even posted them off. This makes me more determined to find a substitute. If I get lucky and the correct sensor arrives I will be able to compare orientation, I cant see any reason the Vectra sensor does not work unless the later model sensor produces less output by design or it is faulty. Thanks for the orientation picture I do understand the importance of the magnetic flux lines being cut across. I guess its possible the Vectra fixing is 90 degrees different but my bet is the hubs castings and drillings are identical but I will check if volts increase with rotation. Other stuff has got in the way but I hope to have time to go looking for the ABS computer. I have to be careful as would you believe the seat belt tensioners are operated by a squib so something as simple as removing a seat can take your hand off.
 

·
Registered
Joined
·
195 Posts
Discussion Starter #18
Hi, Quick update but no progress. Initially when I connected the Vectra Sensor the ABS reset but reappeared on movement, with the cavalier sensor the ABS would not reset itself. I now have the correct genuine GM replacement same make as original, It generates twice the amount of voltage on a wheel spin, Resistance is in range but ABS wont reset its self and I have tried disconnecting battery. I have just sent off for a better code reader that will reset ABS which mine wont.
Its possible the cavalier sensor was OK but required resetting by coder. Although both Cavalier and Vectra sensors seemed down on voltage. As far as magnet orientation etc all of the above sensors look the same. Will report back when Code Reset device arrives. Incidentally the ABS computer is not under the seat so I still don't know where it is.
 

·
Premium Member
Joined
·
574 Posts
Well you've pretty much proved that there is definitely something either wrong with the other sensors, or that they are just not either lining up or are too far away from the toothed ring to generate the required voltage or an out of phase voltage for the ABS ECU to read. Now that you have a correct sensor, you can see what the voltage is supposed to be. Remember, in a previous post you stated something to the effect of that both the front sensors were giving low voltage outputs (0.2 to 0.4 volts), which I took to mean both the offside and the nearside. This would indicate that you have a faulty sensor on each side and need to replace them both, otherwise the light will still come back on as you drive off and the ABS function will still be inoperative. You may think that this is daft, but I had three sensors fail all at the same time, which could be a very unlikely coincidence, but I blamed the fact that I'd pulled and re-seated relays with the battery still connected and also possibly the ignition switched on. It does warn in the manual about disconnecting the battery BEFORE working on the ABS, but sometimes we think we know better than the manual.

If it's really true that those readings from each side of the car are correct, then you have two faulty sensors to replace and not just one. You can rule out one of the rear sensors, as it seems that the speedo gets its signal from one of them and you would know if your speedo wasn't working. A little bit of research I did, indicates that the ABS ECU is known to be possibly unreliable in the face-lift Omega B, but the fault you describe would indicate to me that the problem is with the sensors and not the ECU.

I don't know where the ABS ECU is on the Omega B, and was only guessing that it could possibly be the same as the Carlton Omega A, which is under the nearside front seat, which doesn't have to be removed, but just slid all the way fully forward on its runners, however, your manual should surely indicate where it is on your car.
 

·
Registered
Joined
·
195 Posts
Discussion Starter #20
Hi HMK thanks for responding, Its easy to get this wrong because most Digital Voltmeters auto range but the front left originally produced from memory something like 418 milli volts ie 0.4 of a volt. This lines up with info on you tube suggesting 200 to 400 Millivolts AC. The first two replacement sensors were a bit below these figures suggesting they were faulty, nothing to do with proximity and orientation which I have checked. Question is what voltage were you expecting? Re the position of ABS computer I say again Haines never produced a manual for the facelift and the GM manual just says if light comes up visit your main dealer. I did try refitting the Vectra sensor to see if it reset the computer as it did first time round but with no success. Hopefully all will resolve when my new code reader arrives
 
1 - 20 of 23 Posts
Top