How do i test for ABS fault using a Multi meter?

TehAgent · Unread post by **TehAgent** » 28 Apr 2007, 14:18

I have a LASER multi meter, and need to test a ABS fault using it.

How do i use the meter, and what and were do i test to find out what sensor is at fault,

Basically I'm a real noobie at this, so need to know how to use the meter... IE what settings and were the black and red wire should be attached to it to.

TehAgent · Unread post by **TehAgent** » 28 Apr 2007, 15:03

right, my readings from the car are.

LHF Pins 15 - 30, there was no reading from this.
RHF Pins 1 - 6, 1165 or there abouts ??
RHR Pins 29 - 31, 1090 ish
LHR Pins 19 - 28, 1090 ish

So i take it, its the passenger side front that's borked?

also, is the drivers side one, supposed to be reading so high? or is that one borked too?

Unread post by **Peter.N.** » 28 Apr 2007, 15:09

Firstly you need to find the wires that come from the sensors on the computer input plug, that I cant help you with I'm afraid, although I am sure someone on here can. Then you need to set your meter to the 'resistance' or 'ohms' range and measure the resistance from each wire to earth. I think they should be somewhere between 100 and 200 ohms. if any one lead deviates markedly from this you have a problem. The most likely thing you will find is that you get no reading at all, not 000 that means you have a dead short, but no reading, this usually indicates a broken wire or poor connection to that particular sensor.

Unread post by **Peter.N.** » 28 Apr 2007, 15:10

There you are, the have done it while I was typing!

Unread post by **Peter.N.** » 28 Apr 2007, 15:15

If at least two of them are reading about 1000 ohms, that's obviously what they should be. The one with no reading probably has a break in the wire, the one reading 1165 may have a high resistance connection but I would have thought it would be near enough to work.

TehAgent · Unread post by **TehAgent** » 28 Apr 2007, 16:29

Yay, now all i need to do, is get a replacement sensor, and fit the bugger.

Is it a easy job to replace? i visited the local scrap yard to see how easy they are, but because the car was on the floor, i had limited access to the wire.

I managed to get the scrapyard car sensor off, but as stated, the wiring was a different kettle of fish

Unread post by **Peter.N.** » 28 Apr 2007, 19:56

You were lucky! they usually break when you try to get them out. The usual place for a bad connection is at the junction of the wire from the sensor and to the loom, so assuming that you disconnected it there, just give it a good clean and grease before you put it together.

TehAgent · Unread post by **TehAgent** » 28 Apr 2007, 23:07

If you take the brake disk off the front to get more room, you can loosen the 10mm nut that holds the protection plate on, then move that out the way, and undo the 10mm retaining bolt for the sensor.

then tapping lightly on the sensor its self, you can loosen it from the bracket its mounted on, then its just a case of uncoupling the cable, but as i said, i couldn't gain access to the wire, once it had disappeared into the wheel arch.

I'm not sure if this is the correct way, but it worked on a car that was un road worthy.

Past experience has taught me that, its always best to attempt something like that on a scrap yard car, then attempt it on your own and cock it up.

Unread post by **Peter.N.** » 28 Apr 2007, 23:16

Maybe they have changed them, but I remember on the BX it was such a tight fit that it invariably broke when you tried to take it out. I take that you have cut the cable then, I believe its coaxial, so you will have to make a good watertight job of joining it

TehAgent · Unread post by **TehAgent** » 29 Apr 2007, 00:03

naa, im not using the one from the scrap yard, may as well get a new one, least i know its going to last a bit, i just went down the scrappy to preform some surgery on the scrapped car so as not to damage mine while i found out how to remove it