Abs Issues

[Sabre46]

After sorting out my Water pump rattle Ive now got a problem with my ABS ( had this issue for a long time really) THe ABS seems to want to come on at all speeds of braking even walking pace.

Its been on a diagnostic but with no clear results. Any ideas?

[IanXT4]

Can you elaborate what you mean by "a diagnostic" and is this a 1992 RAV4 as per your details?

[shcm]

Cracked tooth ring perhaps? Odd, because as part of the self-test, there's very often a wheelspeed test/check on each wheel as the vehicle moves off after ignition on. i.e. to simplify it a bit, that all wheels have roughly the same speed.

It must think one wheel is moving slower/faster or locking with respect to the others to generate an ABS event.

[Sabre46]

Can you elaborate what you mean by "a diagnostic" and is this a 1992 RAV4 as per your details?

Its a 1998 2lt Petrol.

By diagnostic I mean the bloke at the garage plugged it in to a diagnostic machine and it "diagnosed" the fault codes. I am trying to up load a print out of the readings. Ill post it up once I have managed to do it. here is the link to the photo og the diagnostic report http://yfrog.com/g0cz5ggvj

[IanXT4]

Hi

You mentioned in your previous post

"Its been on a diagnostic but with no clear results."

What made your "bloke at the garage" not investigate the cause of fault codes, did they successfully clear and not come back ?

[Sabre46]

He was doing another job for me at the time - another vehicle- so I asked if he wouldnt mind running the diagnostic on the RAV as I had this problem with the ABS. He said that when he ran the scan It didnt show anything up but when he printed the result this is what it printed. I dont really understand how these things work and dont really understand what the print out is saying other than a load of things seem to be wrong at the same time, which is unlikeley.

I know I can check the speed sensors with a Multi Meter but can I also check the reluctors in the hubs? Could it be a bit of crap in the hub preventing a clear read by the speed sensor. Just to be able to find out which wheel to look at would be a start!

Thanks for your help

[jedi134]

My freelander pulsated the ABS all the time when the FR sensor was not in properly, it was too far out of the hub..............ABS would come on under normal breaking.

Could also be a bit of rust in there?

[anchorman]

You can't test the rings with a multimeter but you might be able to see them if you get down close and turn the wheel. Like shcm I think that one of them is split or damaged.

I really don't think your RAV ABS is posh enough to be able to store fault codes.

[Sabre46]

You can't test the rings with a multimeter but you might be able to see them if you get down close and turn the wheel. Like shcm I think that one of them is split or damaged.

I really don't think your RAV ABS is posh enough to be able to store fault codes.

I meant that you can test the speed sensor with a multi meter using the Ohms setting to check the resistance.

As for storing codes you may well be right but if you take a look at the picture of the read out, could you tell me what that means?

[IanXT4]

To Save everyone reading the picture at 90 degrees I have typed it out

3 faults found

Code001:

31 FR Wheel VSS Signal abnormal

Code002:

32 FL Wheel VSS Signal abnormal

Code003:

14 Brake master pump relay circuit short to power

1) Motor relay(Stick in on)

2) Circuit and connector between ABS actuator and ECU open and short

3) Module fault

[Sabre46]

Can anyone make sense of that. I cant but then Im not a Toyota mechanic. I see the bit about the relay being open, could tghis be a fault withthe relay and how would I check it?

[Sabre46]

On Saturday I cleaned the front speed sensors as best I could with them still being in the hub. I could not easily remove them from their respective hubs without applying brute force and I was reluctant to do that. I then took it out for a test run and braking hard at about 50MPH. THe front right locks up so I guess this points to this wheel. Question is what is causing the problem? Is it the Sensor - I can test that with a multi meter. PITA to get to the loom conector.

The hub pick up ring - cant see it without dismantelling the hub

Fault in the electronics - how do I check to pinpoint the problem?

Short of taking it to a Toyota dealer and lots of ££££££ Im out of ideas.

[shcm]

Some of this may be obvious, so apologies, but I would expect the following.

First, at ignition on, does the ABS warning light come on and then go off? Or does it go off once you start to move?

If it doesn't come on at all, is the bulb there? If it goes off before you move, the ECU is probably OK. If it doesn't go off, we can't conclude anything about the fault.

Generally there are two type of sensors used for ABS/VSC. Earlier vehicles are very often VR (Variable reluctance) or "passive" sensors. The sensor is basically a coil of wire. You can probably check it by measuring the resistance between two connector pins. Off the top of my head, I'd kind of expect something in the range of 10s to 100s of ohms, but not short or open circuit. This still doesn't guarantee it is OK. It may look OK, but go open/short under vibration from vehicle movement, but it can give you a "warm feeling". I'd expect this kind of sensor on this vintage of RAV, but I haven't checked.

The second type are hall effect or sometimes called "active" sensors. Called active because they need a power supply. A resistance check won't show you much here. Spinning the wheel with the system active, may show you a pulse output, or spinning slowly, might show a voltage change on the sensor output, possibly between about 0 and 5V.

VR sensors are generally robust, but don't work down to zero wheel speed. Hall effects do work down to zero speed and is why they now tend to be used, so that functions like hill hold can be implemented (you need to detect very slow vehicle movements to do that).

To be honest, you probably need all the faults clearing (*maybe* a Battery disconnect would do it), then see which ones come back.

The pump/motor supply fault (if it comes back) may just be a relay somewhere and I'd expect the ABS to do nothing without that fixing. I'd also expect the whole ABS system to shutdown with any fault detected and put the warning light on, so locking a wheel, kind of proves nothing in my opinion.

Sometimes you can read faults with warning lamp flash codes.

[Sabre46]

Some of this may be obvious, so apologies, but I would expect the following.

First, at ignition on, does the ABS warning light come on and then go off? Or does it go off once you start to move?

Comes on then goes off before I start to move.

Generally there are two type of sensors used for ABS/VSC. Earlier vehicles are very often VR (Variable reluctance) or "passive" sensors. The sensor is basically a coil of wire. You can probably check it by measuring the resistance between two connector pins. Off the top of my head, I'd kind of expect something in the range of 10s to 100s of ohms, but not short or open circuit. This still doesn't guarantee it is OK. It may look OK, but go open/short under vibration from vehicle movement, but it can give you a "warm feeling". I'd expect this kind of sensor on this vintage of RAV, but I haven't checked.

The second type are hall effect or sometimes called "active" sensors. Called active because they need a power supply. A resistance check won't show you much here. Spinning the wheel with the system active, may show you a pulse output, or spinning slowly, might show a voltage change on the sensor output, possibly between about 0 and 5V.

VR sensors are generally robust, but don't work down to zero wheel speed. Hall effects do work down to zero speed and is why they now tend to be used, so that functions like hill hold can be implemented (you need to detect very slow vehicle movements to do that).

To be honest, you probably need all the faults clearing (*maybe* a battery disconnect would do it), then see which ones come back.

The pump/motor supply fault (if it comes back) may just be a relay somewhere and I'd expect the ABS to do nothing without that fixing. I'd also expect the whole ABS system to shutdown with any fault detected and put the warning light on, so locking a wheel, kind of proves nothing in my opinion.

Sometimes you can read faults with warning lamp flash codes.

Thanks for your help. The warning light doesnt come on other than at start up. However, It did come on when I was driving up the motortway for 2 hours in minus 5 conditions. It cleared after a pit stop at the services then came on again after a few miles on the same journey. It then cleared when I used the car the next day. But other than that it dosent come on.

[Sabre46]

I drove up the motorway yesterday for about two hours and the ABS light came on for about 20 miles towards the end of the drive but then went off again. Didnt come on on the journey home. Im thinking maybe some thing is vibrating loose?????