ABS warning on standstill / stationary / car not moving

Talk about the 406's electrical system, what wires do what, how to add extra functionality, etc.

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Snook1
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Posts: 5
Joined: Wed Jul 23, 2014 12:20 am

ABS warning on standstill / stationary / car not moving

Post by Snook1 » Thu Jun 15, 2017 3:57 pm

Hi!

Ok, this has been a problem on and off for over a year now.

Last year I took it to a garage and they replaced the ABS sensor on the rear right side, a couple of days later I had the same warning come up so they obviously didn't fix the problem and I was £80 out of pocket, I told them and they said it could be another sensor.. grrr.. which I have my doubts over. The problem then went away for a while but now and then it would come back. Re-starting the car fixes it. Recently it has started to become more frequent, and I have an MOT in a couple of months.

It happens when the car isn't moving so it makes me think that it could be something other than one of the sensors. If it were an ABS ring it would only occur when the car is on motion right? Also I think the ABS sensors only produce a signal when the wheel/ring is moving, so it makes me think it's something else.

I read somewhere, which I can't seem to find now, that there is wiring under the carpet in the drivers footwell which can be compromised, but I've no idea. Anyone had this issue before? I'd hate to pay the garage to have another sensor replaced only to still have this issue.

Thanks

Snook1
Newbie
Posts: 5
Joined: Wed Jul 23, 2014 12:20 am

Re: ABS warning on standstill / stationary / car not moving

Post by Snook1 » Thu Jun 15, 2017 7:13 pm

Ok, so I think I've figured this out myself, so I'm posting this to help others.

The ABS control module, which is connected to the ABS pump (next to the car battery) has a connector on it that looks a bit like a scart lead, the pins inside this connector had oxidisation covering them, likely due to the car being 16 years old.

To release the connector so you can see the pins there is a red clip that slides into the side of it, slide this out to the side and you should be able to pull the black connector upwards and off. I used a small fine nail file and rubbed off this layer of white oxidisation which created a bit of white dust inside the connector which I blew out. I also used some electrical contact cleaning spray which I got from Euro car parts and sprayed this on the pins and into the plug. For the plug I used a sewing needle to push into the connecter pins to help remove and oxidisation there, which is hard to actually see if there was any. Sorry if my lingo isn't quite right, it's hard to know what to describe each bit as!

Hopefully this has solved my issue. I seems pretty obvious but considering the garage didn't do this and I couldn't find this solution online it's worth mentioning it. Pretty sure this oxidisation would have a negative effect on the braking system as there was clearly a white layer of oxidisation which would have compromised the connections to the ABS control system. I think the ABS sensors work by reading a variant impedance or resistance as the wheel spins, an impedance or resistance which will always be present to some degree even when the wheel isn't turning, so if any connection is compromised it would affect this impedance/resistance therefore I'd assume it to give off a fault similar to a sensor fault or a sensor being disconnected.

This should be the first thing to check for rather than replacing ABS sensors.

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