Abs brake fault light
 

I guess this has been covered alot before but my Zt has now got the Abs warning light with the handbrake light on after me disconnecting the battery .
The LCD screen also comes up with the brake fault message temporarily as well.
Can't quite figure it out, didn't have before disconnecting the battery ??
Still got speedo and cruise control so I'm assuming it's either worn brake pads
or a dud rear sensor?
Only thing I did was wash a small amount of battery acid out of the battery tray so hope I haven't upset the abs pump ?

Ive been having ABS problems for a while mainly because time is a bit of a premium for me ...Up to now ive replaced front sensors & bearings...My speedo & cruise were fine until the drivers side bearing went....Im now waiting to hitch it up with a T4 to sort it out once & for all

Took the car to the mechanics today.
They checked all the sensors and all appear to be fine but did say the rear rotors and pads need changing.
Pulled the plug on the Abs module, they gave it a clean but still have the Abs and brake light warning on.
Their diagnostic system came up with the same fault "OE-valve relay error"
as TOAF did which I think relates to the Abs module.
Took it to local auto electricians to see if it is a voltage feed issue ( although the wiring loom looks fine) but they basically said they couldn't do anything unless they had the right voltages on the pinouts as it is an usual car over here and they have no data.
I think the relay is inside the pump module and maybe this is not working.
I guess the next thing to do is get a used abs pump and see if that fixes it.
Any other ideas welcome.
I feel this is not going to be a cheap fix !!!

Washing battery acid off the tray? Oh dear, the ABS block sits just behind and below the battery tray and is known to suffer wiring damage or bad connections. Remove the battery, tray, etc so you can get to it and try disconnecting/reconnecting the multiplug several times to see if that improves things. It not, at least you'll now have access to swap it out.

There was not much battery acid in the bottom of the tray and no signs of it on the abs but only washed it using a sponge so there shouldn't have been much water .Wiring loom looks as new.The plug is pretty well sealed.
Have the abs pump module plug off a couple of times , cleaned it etc but still the brake fault and abs light remains.
Read a similar post where a 75 car had the same issue,testing came up with abs module fault poster had car checked by a garage , spent a fortune on checks, sensors apparently were tested ok , in the end the guy got rid of the car because cost of replacing the abs module only to find the new owner got it fixed by replacing a wheel sensor.
As both the warning lights stay on when started I'm wondering if it may be a sensor as the abs system would need the wheels to rotate to register anything I would think. The fact that both the brake fault and abs lights come on same time is strange and the fact that I still have a working speedo and cruise control seems to suggest the front speed sensor is working.
Hoping it may be rear sensors. Seems this fault has done a few peoples heads in.

Check underbonnet fusebox for blown fuses. If there's a relay there for ABS (I think there is) then swap it with the same type from another circuit - don't forget the loom under the fusebox chafes on the seam of the chassis member. It's very unlikely to be a sensor because a) unless they were open or short circuit they'd only cause ABS light when you start moving, and b) there are specific error messages for sensor faults. Your fault code indicates something wrong with the valve block itself, most likely power supply related, so you need to be checking both for 12V from the ABS relay when ignition on, and a good earth connection. You really need a multimeter and the ABS circuit diagram from RAVE, though a quicker test is simply plug in an alternative ABS block (doesn't need to be plumbed in) and see if you get the same fault.

Great stuff gents, I went out today and connected an old Abs plug I had and firstly connected it directly to the car side (abs module side) and got a reading of 11.33 volts each plug when turning the ignition on.
Then went and connected all the plugs back together again and got a reading of about 1.6 volts on one wire of each of the plugs.
That was having the negative of the voltmeter grounded to the chassis .
Not sure but seems to me the abs module is at least sending voltage to all the 4
sensors and if I'm getting about 1.6 volts from the sensors that should be in spec.
I did try measuring across the 2 wires with the rear sensors disconnected but didn't appear to get anything but figured as it is a hall sensor type device I probably wouldn't get any reading unless the wheels were moving .
Just ordered a new set of rear disc and pads so will get my mechanic
( one of your countryman - gentleman and scholar) to have a look when fitting the brakes and see what I beed to buy next.

That's a bunch of great info re the abs sensors.
Did you do any voltage readings from the car (abs module) side of the plugs ?
I got a reading of 11.33 volts on each plug when I switched the ignition on so I'm hoping that means the abs module is working ? Which may indicate it is a sensor ?

Not sure if this would work try connecting the abs plug pins at each wheel in turn to make them open circuit and see what happens as said not even sure if this would actually work or may even cause further probs hopefully someone can verify this procedure.

Would be great if some one can document what voltages a working Abs module
delivers to the plug (sensors) unplugged .
If we can ascertain that ,anyone with a similar question ,Is the abs module working properly ? , it could checked pretty easily without pulling the module out.