Yaris brake judder problem

[barrygadd2003]

Help... I'm trying to sort my 2002 Yaris (French model) where the brakes judder on low speed braking.At no time does the ABS waring light show.

I've checked:-

Each sensor with a multimeter. Each gives a signal around 0.2 to 1v.

A friendly garage mechanic attached his Bosch diagnostic tester via the OBD2 connector while I drove the car. 3 displayed sensor signals were much the same but the front passenger signal was noticeably different.

I replaced this sensor with a new Bosch replacement sensor but the problem is still there

I'm now stuck as to what to do next.

(I've even removed the 60A ABS fuse but this caused both the ABS warning light and brake warning lights to light up. 

My main aim is to get the car through the MOT

Has anybody know what the problem is?  I'm very happy to tackle whatever the job is as I've been working on cars and bikes for the last 50 years (not professionally).

Out of interest, if the abs pump/module is faulty would this cause the effect? and if the unit is the problem would it always cause the ABS light to show? 

[PaulinhoT]

Hello and welcome to the T.O.C 😄

Does the brake judder come through the steering wheel ?

[barrygadd2003]

Hi, Thanks for getting back to me. There is no noticeable judder/movement of the steering wheel during the braking judder. This is my first car with electric PAS and although with normal driving it does feel slightly different from hydraulic PAS, it doesn't react with the braking problem. The problem seems to be confined to low speed braking and I can hear a juddering noise from under the bonnet and it appears to come from the pump/ABS solenoid unit. What I will do is to get a friend to drive the car slowly with the bonnet up while I look and listen to the ABS unit. (Sounds dodgy but at low speed down the drive It should be fun.....)

[PaulinhoT]

Let me know what you find okay 😄

[FROSTYBALLS]

Moved to the Yaris club.

[m456an]

Have the brake drums been serviced? If the noise is traveling from front brakes through suspension to bonnet it may be wise to service the front brakes. Copper grease on outside of pad, red rubber grease on pistons.

https://mycarneedsa.com/blog/causes-of-brake-judder-and-how-to-fix-it

[bathtub tom]

I think the sensors and surrounding area need to be very clean to ensure the sensor sits in the correct position. You could try swapping front sensors, but then you'd need your friendly mechanics OBD reader to see if the dodgy reading moves.

[mrfixer]

Is the judder caused by the ABS operating?

Remove the fuse to disable the ABS. If you still have judder it is not ABS but rather caliper/disc/pad or some other problem.

If it is ABS prematurely operating at low speed then a low wheel speed signal is most likely. Check wheel speed signals and looked for cracked/corroded reluctor rings. A hairline crack will stop the ring working properly.

[barrygadd2003]

Hi Many thanks for your reply. I've had all 4 brakes apart and replaced the rear shoes.The rear brakes look fine. I've also taken the fronts apart. The front pads look fine as do the discs. I've pushed in the caliper pistons to ensure these are free and dribbled a couple of drops of brake fluid under the rubber piston cover to ensure free movement.I've taken out the pads and freed up the movement of the pads in the caliper which also slides freely as it should..All to no avail!!! I've now taken the car to a mechanic friend with a  very impressive diagnostic kit and am hoping he can find the problem. The problem is, I can reproduce the brake judder here at home regularly but at the mechanics garage the problem doesn't show itself. (this is driving me nuts!!)

A couple of queries  :-

Could the ABS pump assembly cause this effect? At no time has there been an ABS warning light on the dash

What effect would old(ish)/grubby looking brake fluid have on brake behaviour (or clutch)

[barrygadd2003]

Many thanks for the above replies. I left my Yaris with the friendly mechanic who after driving a short while experienced the slow speed brake judder. He took both front sensors out and as I had done with the nearside securing 6mm bolt also sheared the head off.(the driver side) He was concerned the sensors may not be sitting in their original positions due to rust build up in the mounting holes.He used a bur attached to a flexi drive and cleared out any rust build up around the sensor mounting. THIS DID THE TRICK. I collected the car yesterday and the juddering has stopped. Fingers crossed the problem won't return but looking good so far.

SECOND YARIS PROBLEM

I hope I'm not contravening club rules by describing another problem.  I bought the Yaris in April and the engine warning light was and remains, on. The code is P0141 (heated post cat sensor) Looking at previous MOT's this has been mentioned during previous years but as the car is registered in 2002 does not constitute a failure as the post cat regulation only started in 2003. BUT I'd like to sort this out rather than seeing a warning light. My mechanic friend using his diagnostic set up advises there is nothing wrong with the actual sensor. Anybody got any ideas what may be causing the light to  come on???

[m456an]

If there is nothing wrong, than cataclean would be the next step, I would not bother with anything else if that does not work. The important thing is the judder has gone.

[riso]

On 6/28/2019 at 9:17 AM, barrygadd2003 said:

Many thanks for the above replies. I left my Yaris with the friendly mechanic who after driving a short while experienced the slow speed brake judder. He took both front sensors out and as I had done with the nearside securing 6mm bolt also sheared the head off.(the driver side) He was concerned the sensors may not be sitting in their original positions due to rust build up in the mounting holes.He used a bur attached to a flexi drive and cleared out any rust build up around the sensor mounting. THIS DID THE TRICK. I collected the car yesterday and the juddering has stopped. Fingers crossed the problem won't return but looking good so far.

SECOND YARIS PROBLEM

I hope I'm not contravening club rules by describing another problem.  I bought the Yaris in April and the engine warning light was and remains, on. The code is P0141 (heated post cat sensor) Looking at previous MOT's this has been mentioned during previous years but as the car is registered in 2002 does not constitute a failure as the post cat regulation only started in 2003. BUT I'd like to sort this out rather than seeing a warning light. My mechanic friend using his diagnostic set up advises there is nothing wrong with the actual sensor. Anybody got any ideas what may be causing the light to  come on???

Hello Barry - I'm having the same problem with my 2003 Yaris and haven't found a mechanic who can fix it.. I'm not far from Surrey and wondered if you'd pass on details for your 'friendly mechanic' !  Thanks