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ABS sensor voltage ballpark


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Hi people, been a while since I've been on here but I need some help. On my 2000 1.3 sr jap built P1 yaris the abs has been coming on around 70% of the time I press the brakes under normal braking conditions. Pulling the abs fuse in the cabin fuse box has disabled the abs, illuminated the abs warning light and stopped the problem. Trying to find the problem is tested the front abs sensors with the front jacked up and in 4th gear and got 1.3V on the right front and sensor plug and 2.7V on the front right. Hanyes manual says 1.5-2.0V so one is too high and the other too low! Unsure how I can test the rear as the sensor is pressed into the rear hub and i cant trace the connector plug to see wjere it is to trace it. Any ideas? I do not know which wheel the abs is activiating on as i dont know how i would find that out.

Thanks for any responses.

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You either need a scan tool so you can see the data and/or an oscilloscope to see the wave form - any abs codes stored ??

How do the wheel bearings feel ? It may be the abs ring in the bearing (replace the hub as a unit)

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2 minutes ago, flash22 said:

you either need a scan tool so you can see the data and/or an oscilloscope to see the wave form - any abs codes stored ??

how do the wheel bearing feel ? it may be the abs ring in the bearing (replace the hub as a unit)

I don't have an obd reader or an oscilloscope so unsure if there are any stored codes. Wheel bearings feel fine no play in the wheels that I have noticed or any noise. However, I haven't specifically checked that so will do that today.

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The sensors are piezoelectric that is activated by a segmented ring, a meter will not be able to pick up if the magnet is bad, A abs capable scan tool is needed to determine if the sensors are reading correctly at the same rates

IIRC the rear sensor and ring are part of the bearing you just replace the whole hub

 

You could check the resistants/impedance of each sensor

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Just remembered you can do the paper clip test

link pins CG and TC and turn on the ignition the  abs will flash a 2-digit code - light goes off for 2 seconds then count the flashes - Then the light goes off for 2 seconds, then count the flashes for the second digit

 

1845520523_ABSpaperclip.thumb.jpg.8931eae9d217b0bbbfaeee9a0998a29d.jpg

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2 hours ago, flash22 said:

The sensors are piezoelectric that is activated by a segmented ring, a meter will not be able to pick up if the magnet is bad, A abs capable scan tool is needed to determine if the sensors are reading correctly at the same rates

IIRC the rear sensor and ring are part of the bearing you just replace the whole hub

 

You could check the resistants/impedance of each sensor

The last sentence when you say I could check the resistance of each sensor sounds like my next step and your most recent post about the paper clip test sounds a bit beyond my current skill level. My aim is to determine which abs sensor/ ring is not working correctly so testing the resistance of each one should tell me this? Where are the plugs for the rear sensors located so I can check them if I have understood correctly?

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The paper clip test is very easy - you only learn new skills by doing them

 

iirc the sensors are in the back of the hub it will only tell you if the sensor is any good as you getting an abs activation the sensor must be working

example. https://www.ebay.co.uk/itm/REAR-WHEEL-HUB-BEARING-WITH-ABS-FOR-TOYOTA-YARIS-99-05-SCION-ECHO-SCION-VITZ-/123739062786

 

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I had exactly the same difficulty finding which wheel was giving the fault. I was reluctant to pay for a full diagnostic sya £60, which may or may not have detected the faulty ABS. I would have installed Techstream for Toyota on my laptop frpom these people https://ps-cardiagnostics.com

but my laptop was the wriong spec so I got a local car shop to drive around their car park and immediately identified a rear sensor which is integral to the hub for a modest £25 charge. The new hub was about £30. Along the way i replaced both front sensors fpr £30,and they were choked up with rust flakes. Both front sensor securing bolts sheared off and I had to drill and retap for new screws.

Good luck with it; it is a test fail so you need to get on with it. Techstream is £12.99 -well worth the money if you have old Toyotas!

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1 hour ago, sproutdreamer said:

I had exactly the same difficulty finding which wheel was giving the fault. I was reluctant to pay for a full diagnostic sya £60, which may or may not have detected the faulty ABS. I would have installed Techstream for Toyota on my laptop frpom these people https://ps-cardiagnostics.com

but my laptop was the wriong spec so I got a local car shop to drive around their car park and immediately identified a rear sensor which is integral to the hub for a modest £25 charge. The new hub was about £30. Along the way i replaced both front sensors fpr £30,and they were choked up with rust flakes. Both front sensor securing bolts sheared off and I had to drill and retap for new screws.

Good luck with it; it is a test fail so you need to get on with it. Techstream is £12.99 -well worth the money if you have old Toyotas!

Thank you I will have a look at techstream. I'm guessing the car shop used one of their scanning tools to identify which abs was faulty?

Thanks for the heads up about the front sensor bolts, I have heard this before so have been spraying them with penetrating fluid past few days in case I need to get at them

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1 hour ago, FirstCarFirstYaris said:

Thank you I will have a look at techstream.

Techstream is a great tool, no question.  But, I bought a cable/CD etc off eBay and although it worked perfectly on our newer cars, I never got it to work at all on our 2001 Corolla.  I returned the item as defective as it failed its own diagnostic test on some routines, and bought another one off a different seller, but that was exactly the same.  I still have and use that cable, but on newer cars only.

That 2001 Corolla works fine with a generic OBD2 tester plugged in, so the diagnostic port seems to be working 100%.  The older OBD2 spec. (used up until a few years after yours was made) uses different physical pins to communicate down to the OBD2 port (it's called 'K-line', I think), than the later ones. 

I suspect that some of the eBay cables don't accommodate K-line, even though they claim to. Or they didn't a few years back when I bought mine.

Hopefully these problems are resolved now.  Perhaps someone else has recent experience of Techstream on older cars?

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TBH setting up techstream is harder than doing a paper clip test - early OBD2 can be a bit hit-and-miss 2002/3 onwards it all started to become more standardized

i have multiple code readers/scanners what cost me a fair bit of cash

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53 minutes ago, flash22 said:

TBH setting up techstream is harder than doing a paper clip test - early OBD2 can be a bit hit-and-miss 2002/3 onwards it all started to become more standardized

i have multiple code readers/scanners what cost me a fair bit of cash

I did think it was a bit of a gamble getting the software and considering I won't be keeping the car for too much longer I didn't really want to invest in a scanner. Could you please describe the paper clip test or tell me where I can find more in for as I'm not really sure what I'm looking for.

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