ABS sensors

robin hughes · Post by **robin hughes** » Tue Nov 14, 2006 7:00 pm

Whats the quickest and easyest way to test the abs sensors to find out which one is broke without having to pull them off. I havent got a multimeter and my abs light is permanetly on. need to sort the problem out in the next 2 weeks for mot thanks

thanuttiscotsman · Post by **thanuttiscotsman** » Tue Nov 14, 2006 7:16 pm

hi there,
thats an easy one as there are only sensors at the front. just take a spare and try plugging it into either side and you'll soon see which one turns off the abs light.

rossco

jayw · Post by **jayw** » Tue Nov 14, 2006 7:19 pm

The easiest way for me was using the old Resistor trick:

Get a 1k resistor, attach a couple of inches of wire to each end.

Unplug each sensor in turn (fronts by inner arches at back, rears under rear seat) and bridge the connector with the resistor (the inboard cable not the sensor end).

While you're holding it in place get your assistant to switch the ignition on. When you've found the faulty sensor the light will go out.

The fronts are a doddle, but the rears are a pig to change usually.

The good thing is that you can then tape the resistor in place and leave it there for the MOT. The light remains off unless you drive off and over 7mph i think it is which is fine if you're parking right outside the test station (or driving it in yourself).

Both my cars have been through the MOT like this (both fixed now)

If you need a resistor let me know your address as i've got loads as i was going to make a batch up & sell them on ebay as quick-fixes.

Thats all assuming it's a sensor fault...

Cheers, Jay

Post by **Adrian E** » Tue Nov 14, 2006 11:28 pm

Rossco

There are sensors on the back - the connectors are under the back seat, if you need to get to them for fault finding.

thanuttiscotsman · Post by **thanuttiscotsman** » Wed Nov 15, 2006 8:01 am

Adrian E wrote:Rossco

There are sensors on the back - the connectors are under the back seat, if you need to get to them for fault finding.

hi adrian,
thanks thats good to know.!! as my abs light is on because a sensor is at fault!! would have taken me years to find which one if i wasnt looking in all the right places. but surely still all the connecting plugs being the same just the shape and fitting different, surely the easyest way to test is by plugging a spare one into all the plugs one after other till light goes out.?

cheers rossco

Anonymous · Post by **Anonymous** » Wed Nov 15, 2006 9:09 am

Wilkinsons sell multimeters for just £7.95. One summer, whilst working as a school science techninician, I tested thirty-odd cheap multimeters against a standard cell (accurate to two .001volt at room temp): all of the cheap meters were spot-on and read exactly the same. Modern electronics are amazing........
ABS sensors usually seem to fail at lead wire or connector, rather than at the windings, making repair sometimes possible.

Post by **Adrian E** » Wed Nov 15, 2006 9:46 am

Yep, connectors are all the same so assuming (a) your fault light comes on when you first start the car rather than when it's been moved and (b) the spare sensor you've got is known good then you can just plug in a replacement until you find the duff one(s)

Multimeter is far more reliable method, especially if you suspect more than one dodgy sensor.

Adrian

jayw · Post by **jayw** » Wed Nov 15, 2006 2:36 pm

Thats all assuming that you have a 'spare' sensor that you know is good to test with

thanuttiscotsman · Post by **thanuttiscotsman** » Wed Nov 15, 2006 2:43 pm

hi there,
would it not be even easier to just drive down the road and hammer the brakes on then whichever tyre skids has the dodgy sensor?? as mine has a dodgy one i assume as my lights on but when i drive it in the car park and hit the brakes it sometimes skids but only the front right wheel iirc.?

cheers rossco

Post by **Jezziebx16v** » Wed Nov 15, 2006 3:15 pm

thanuttiscotsman wrote:hi there,
would it not be even easier to just drive down the road and hammer the brakes on then whichever tyre skids has the dodgy sensor?? as mine has a dodgy one i assume as my lights on but when i drive it in the car park and hit the brakes it sometimes skids but only the front right wheel iirc.?

cheers rossco

As far as i know if the ABS light is on you aint got no ABS full stop, if only things were as easy as you suggest.

Jez

robin hughes · Post by **robin hughes** » Wed Nov 15, 2006 3:18 pm

The abs sensor i have to fit is brand new

will do it this weekend. Thanks for your help guys

Timmo · Post by **Timmo** » Wed Nov 15, 2006 4:15 pm

yeah if the light is on you dont have abs!!
they are a simple swap over when you find the iffy one!
sorry rob i cant make it up this weekend matey! bit strapped for cash at the mo! what with a potentially dead fiat (box needs to come of!)and cartax for mine due!
may be i should find some paying customers cars to clean! loL!

ed_straker · Post by **ed_straker** » Wed Nov 15, 2006 4:18 pm

Are you sure it's a faulty sensor?!
Had the light on and the garage cleaned sensors and driveshafts and everythings Ok!

Post by **Toddman** » Wed Nov 15, 2006 5:44 pm

ed_straker wrote:Are you sure it's a faulty sensor?!
Had the light on and the garage cleaned sensors and driveshafts and everythings Ok!

That is why the correct method is to use a meter then if no poor resistance readings are found you know it is likely to be the teeth or the air gap. the ABS unit is generally very sturdy and even the ABS relays seem to last a lomng time.

Cheers
Luke

robin hughes · Post by **robin hughes** » Wed Nov 15, 2006 6:38 pm

Ive got a feeling its one of the rear ones. I may have disturbed it while i was dismantling the back end to paint and underseal not to mention if it is theres gallons of waxoyl sprayed all over the place so its going to be a messy job

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