ABS Sensor readings

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dazthephot
Joined: Wed 09 Apr, 2008 18:58
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  Z3 roadster 1.9i
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ABS Sensor readings

Post by dazthephot »

Hi all.

I have yet to buy a code reader so I thought I’d do it old school to see if I have a faulty abs sensor. Trouble is I don’t know what the acceptable range is.

I have approx 1.1k ohms on all but the near side rear which is 1.8k ohms. So is that the suspect one that needs changing or do I need to do another test?

It’s a chore getting all 4 wheels off but it gives me the chance to inspect.

Thanks.


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NZ00Z3
Joined: Thu 23 Jun, 2016 01:26
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  Z3 roadster 3.0i

Re: ABS Sensor readings

Post by NZ00Z3 »

Set your multimeter to AC Volts (auto range) and spin the wheels, you should get a voltage from good sensors.

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dazthephot
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Re: ABS Sensor readings

Post by dazthephot »

NZ00Z3 wrote:Set your multimeter to AC Volts (auto range) and spin the wheels, you should get a voltage from good sensors.
Ok thanks. It’s a right PITA like to access the sensor socket when the wheel is still on plus the pins are male and you can’t get the multimeter probes in. I used a bit of wire on one pin then the probe on the other.


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LaRy
Joined: Mon 12 Nov, 2018 17:47
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  Z3 roadster 2.8

Re: ABS Sensor readings

Post by LaRy »

I think the sensor showing 1.8kOhm is suspect. Normally it should be around 1 kOhm as you have for the others. If you have a ACS/ABS system type Teves Mk IV, the alarm triggering level is set to 2 kOhm. Another thing you should take in consideration is that the accuracy for multimeters in low ohm area is very poor = it could actually be 2 KOhm. Normally you should always use a real low Ohm meter like a Weaston Bridge, but who owns that?
I would definitely change that sensor, an buy a quality one, not some unbranded Chinese made copy.
Most probably this sensor with odd value will also show a big difference in voltage when spinning the wheel.

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pingu
Joined: Fri 30 Apr, 2004 16:01
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Re: ABS Sensor readings

Post by pingu »

Get a salvage BMW one rather than a new copy.
Pingu

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dazthephot
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Re: ABS Sensor readings

Post by dazthephot »

LaRy wrote:I think the sensor showing 1.8kOhm is suspect. Normally it should be around 1 kOhm as you have for the others. If you have a ACS/ABS system type Teves Mk IV, the alarm triggering level is set to 2 kOhm. Another thing you should take in consideration is that the accuracy for multimeters in low ohm area is very poor = it could actually be 2 KOhm. Normally you should always use a real low Ohm meter like a Weaston Bridge, but who owns that?
I would definitely change that sensor, an buy a quality one, not some unbranded Chinese made copy.
Most probably this sensor with odd value will also show a big difference in voltage when spinning the wheel.
Thanks LaRy

I used to have a Fluke but I couldn’t find it so I used my cheapo multimeter which I doubt is very accurate.
I will change that sensor and see what happens.


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dazthephot
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Re: ABS Sensor readings

Post by dazthephot »

pingu wrote:Get a salvage BMW one rather than a new copy.
Thanks I will see if I can get one, there’s quite a few breakers around the internet. Depends on price saving though over a new one. Big breakers give a short warranty though which is good.


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pingu
Joined: Fri 30 Apr, 2004 16:01
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Re: ABS Sensor readings

Post by pingu »

dazthephot wrote:
Mon 12 Aug, 2019 09:32
pingu wrote:Get a salvage BMW one rather than a new copy.
Thanks I will see if I can get one, there’s quite a few breakers around the internet. Depends on price saving though over a new one. Big breakers give a short warranty though which is good.


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It's not the money saving, but the fact it is a BMW sensor that you are buying. I'd easily pay 50% of full BMW new price for a salvaged original.
Pingu

LaRy
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  Z3 roadster 2.8

Re: ABS Sensor readings

Post by LaRy »

My opinion, as long as you buy a sensor manufactured by Hella, Bosch or ATE it will work. I have replaced my front wheel sensor, using an ATE, no problem.

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dazthephot
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Re: ABS Sensor readings

Post by dazthephot »

LaRy wrote:My opinion, as long as you buy a sensor manufactured by Hella, Bosch or ATE it will work. I have replaced my front wheel sensor, using an ATE, no problem.
Hmm well in that case I can get a new Hella one for about £30. Worth a punt maybe?
Bizarre the bloody lights have gone off again.

I’ll be honest if it was the relay I still can’t identify it. There’s certainly no big red one with ABS written on it.


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LaRy
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Re: ABS Sensor readings

Post by LaRy »

https://i.imgur.com/5uE1HOL.jpg

Attaching a picture showing the ABS and ACS relays including text in my fuse box.

LaRy
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  Z3 roadster 2.8

Re: ABS Sensor readings

Post by LaRy »

If both the low beam lights are gone, I would guess relay K48 is broken, the smaller green one, placed to the right in my photo. I had to change mine a couple of years ago.
You can test if the high beam light is working, it is independent of the relay.
Those relays are getting old.
Additional information, the picture is valid for a car produced around 1997 -1998.

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dazthephot
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Re: ABS Sensor readings

Post by dazthephot »

LaRy wrote:https://i.imgur.com/5uE1HOL.jpg

Attaching a picture showing the ABS and ACS relays including text in my fuse box.
Thanks LaRy, a bit different to mine. When I say lights I mean dashboard warning lights. It’s raining today and low and behold the lights have come back on. They went off in the dry. Image


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