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940 940 ABS not working

hessam69

Well-known member
Joined
Jun 19, 2009
Location
Sydney, Australia
Hi,

The 1993 940 I have has a non-functioning ABS.

Even the ABS fault lamp doesn't light up. I have checked the globe and confirmed it is working.

When trying to retrieve the fault codes from the diagnostics socket, there is a faint glow on the red LED, and holding the button for 3 seconds does nothing. I have checked the ABS fuse and it is intact.

Any ideas where to look to next?

Thank you
 
Thank you, have you got a wiring diagram?

Once I have the wiring diagram, how do I use it?

I'm an electronics newb so I need plenty of help.
 
Thank you, have you got a wiring diagram?

Once I have the wiring diagram, how do I use it?

I'm an electronics newb so I need plenty of help.

If you're going to work on your own car, start with an auto mechanics fundamentals book. This is the one I read twice to pound basics into my head (it has a useful basic automotive electronics section with sample wiring diagrams):

https://www.ebay.com.au/itm/Auto-Me...m59234b6ab3:g:vHoAAOSw4EJcjQpC&frcectupt=true

Don't be afraid to ask around for someone with experience to help you in person.
 
Thank you, have you got a wiring diagram?

Once I have the wiring diagram, how do I use it?

I'm an electronics newb so I need plenty of help.

http://borich.lesnoe.spb.ru/auto/Vo...202_940_1994_wiring_diagrams_section_3_39.pdf

Page 134.

I'm not a pro reading diagrams but here's what I think.

You're saying your ABS lamp also doesn't light up.
Together with a non working ABS system, there could be something wrong with the ground wire at the ABS unit, as the bulb ground goes via the unit from what I can see looking at the diagram.
It's a black wire going to the ground point on the inner fender.
I would look at this first.

Did the ABS never work or did it just recently stop?
 
Looking at the next page 135, the black ground wire should go from the side of the ABS unit (8/15) to either ground point (31/2 or 31/1) on the inner fender, depending on which side the unit is located on your car.

I'm not near my car so I can't have a look myself at the moment, sorry.
 
Here's how the ground wire on the ABS unit looks on my 97.

I couldn't get a photo of the ground point because it's a bit hidden on the inner fender down by the battery. That's where it should go.
 

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Mine didn't work for the longest time until once day I had the knee pad off underneath the steering column and noticed this funny looking relay with a fuse holder on it. The fuse was blown so I changed it with no idea what that would even do, lo and behold now my ABS works
 
Do you have a test lamp and a meter?

If not, fire an ABS control unit at the problem. Its a long metal box under the driver side dash.
 
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Get a test lamp and confirm power to each terminal of the power circuits

Use a meter and confirm less than a couple ohms on the ground circuits.
 
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