ABS pump running continuously - help please!

[AndyT5]

Hi All,

Hope someone may have resolved this issue before...

1997 V70 T5.
Car had been standing, locked for about a day, and I suddenly heard the ABS pump running. (Car locked, no key in ignition). I disconnected the battery to limit potential further damage.

I have previously resoldered the ABS unit (about 8 years ago) with success, so resoldered the connector pins again just in case it was that, but no change: ABS pump runs continuously from the moment I connect the battery.

Any thoughts on the issue please? E.g. bigger abs ECU problem, hydraulic pump, or some hidden relay somewhere that I haven't found? I'm thinking it's not a sensor related issue that provides input to the ECU.

Will try and read codes shortly, but need to reassemble first as car needs to be running to read codes...

Any thoughts gratefully received!

Thanks

Andy

[andrewc1267]

Originally Posted by AndyT5

Hi All,

Hope someone may have resolved this issue before...

1997 V70 T5.
Car had been standing, locked for about a day, and I suddenly heard the ABS pump running. (Car locked, no key in ignition). I disconnected the battery to limit potential further damage.

I have previously resoldered the ABS unit (about 8 years ago) with success, so resoldered the connector pins again just in case it was that, but no change: ABS pump runs continuously from the moment I connect the battery.

Any thoughts on the issue please? E.g. bigger abs ECU problem, hydraulic pump, or some hidden relay somewhere that I haven't found? I'm thinking it's not a sensor related issue that provides input to the ECU.

Will try and read codes shortly, but need to reassemble first as car needs to be running to read codes...

Any thoughts gratefully received!

Thanks

Andy

Sounds like you need a replacement or at the least your unit repaired VAG are very common for the same issue and its always the unit

[AndyT5]

Thanks - I'm contemplating sending the unit off for repair, unless someone shortly has had experience of a different resolution for the same issue. Maybe not much point in me reassembling the car for the purpose of just reading the fault codes.

[PNuT]

Not sure you should have power to the ABS pump with ignition off...

I would unplug the abs pump for a start as it is just a simple plug & start checking wiring diagrams!

[AndyT5]

Indeed- I was very surprised. ABS was working fine with no lights or fault codes when it was last driven. Going from that to the ABS pump running with the car still locked blew my mind a bit! I haven't checked the wiring diagram, but if it's correct there is no separate relay, is it possible the ABS ECU does normally always see 12v when battery is connected?

Of course the MOT expiry is now just a month a way!

[4x4]

Check the ABS fuse (number 9 on the 850) not sure if the V70 is the same, should be 30 Amp

[PNuT]

I have just had a look & the abs controller does have a live feed....

But the pump itself is powered thru the abs controller by the looks of it

I would expect the abs ecu is bad!

[AndyT5]

Thanks - that confirms my suspicion. I don't see how it could be anything other than the ECU (unless something else has caused the ECU to fail in the first place). Pump does seem to get its feed direct from ECU.

I briefly looked into fuse related problems - fuse 3 is "ABS". Fuse intact, and no change to behaviour with fuse removed. Perhaps the fuse is only related to the ABS sensors, and not the ECU itself.

Now to choose a reputable rebuild company...
I haven't found any second hand ones located in this country yet PN 9162675. (Apparently 9140774 is also compatible).

[PNuT]

I have both....

If they are any good is another matter!

I assume tracs?

Non tracs will work as well but obviously not the tracs

[Derek UK]

When the pump is running, is the ABS light on? Could one of the sensors be shorted out? Can you disconnect them one by one to check? Putting the blame on the ECU may be correct but I'd be checking other things as well. Something must be triggering the pump to run. Do pistons in the ABS block stick (I've no knowledge of what goes on inside) Bleed the system?