ABS Warning Light
 

Hi,

I was looking for some help with my Rover 75.

The ABS warning light came on a few months ago and initially it would come on and off randomly and usually slamming the brakes enough to induce a skid would clear it.

Recently though, the light has been on constantly.

I checked the sensors today with a ohm meter and they all appear to be fine. I didn't check the nearside front as I have read this drives the speedo and that is working fine.

I think the next step would be to get it on a T4 to try and determine if there are any fault codes and what they are.

Does anyone have any further advice or know of anyone in the Aberdeen/Aberdeenshire area with a T4 that could run the diagnostic?

Thanks for any help.

Ohm meter? If you just checked the resistance of the sensors it won't tell you that much.


With your meter set to volts you can check all the sensors and magnetic reluctor segments in the bearings


The signal voltage changes from 1.7V to 0.7V as each magnetic segment passes the sensor, so jack each wheel in turn and slowly rotate it marking any failures on the tyre wall with chalk.

If the failures are in the same place each revolution then likely a damaged reluctor, and if in random places suspect the sensor or possibly a slightly too big air gap.

Other common failure causes are cable damage to the sensors or corroded plug pins at the ABS modulator.

Here is a front hub being tested prior to fitting. I use an extension cable made up from some old speaker wire and ABS plug and socket which saves pinning through the ABS cables. It also doubles up to allow any sensor to be plugged in to the OSF so that the speedometer can be used as a diagnostic.

[IMG]http://i1108.photobucket.com/albums/...ps40be8806.jpg[/IMG]

Hi,

Thanks for the info.

My thinking was that usually if the sensor has burnt out or the wire from the sensor to the plug was damaged, then the meter would show an open circuit. Unfortunately this wasn't the case.

I don't believe it to be one of the bearings as the abs fault indicator comes in the wee screen in the dash board before the car is moving. I read on some other posts that if it was a bearing, this would be indicated by the abs light going out at the initial start up check but coming on when the car starts moving.

I also checked the plug to the abs module under the battery as I have read corrosion in the contacts can cause issues however I couldn't work out how to remove the plug. I got the cover off but didn't want to pull on anything incase there is a catch or something and I end up breaking it.

I'm thinking now its likely to be the abs module or the wiring between the module and the sensors. I think a T4 session is likely to be the best and easiest way to find out whats going on. Just need to try and find out where has one.

Thanks again for your suggestions.
Glen

PM
 

PM sent re T4 session

Chris

To remove that plug there is a slider clip under the cable of the plug. You will need a very fine grub screwdriver to start it. Pull away from the socket and plug in the direction of the cable, outwards if you like. You will feel it click as it releases the plug from the socket. There will be NO resistance to remove the plug. Be very carefully the pins are very small and thin.