1994 Help fixing ABS pump

nut3y

So my 850 has been throwing DTC code 443 for the ABS system, saying there is an ABS Pump failure. The service manual says that if the computer detects a voltage between the two blue wires that is less than 500mV AC it will throw the code. I've worked through the given troubleshooting steps and this is the only thing that isn't to spec, instead reading ~30-200mV. The motors brushes are fine and the motor still runs as it should with the power cables hooked up to battery voltage. Tearing down the motor I've discovered that the blue leads run to two pins on the motor housing which go into this little plastic thingy. Continuity is fine between the female pins and the blue leads so breaks in the connection aren't the issue. The plastic thingy has a little metal insert that just sits there without any connection to anything so I'm stumped as to how this works or how to get the voltage up to 500mV. Just wondering if anyone has experience with these or any tips on how to get the voltage above 500mV? Just not keen on dropping $220 on a used pump modulator that might not even work when this one at least spins.

Motor Internals

Female connector pins

4 pin plug (what's left of it)

ABS Modulator

Magical plastic thing

ramrod

Have you already repaired the module? They are all known for having dry joints in the board

timbo

ramrod
Have you already repaired the module? They are all known for having dry joints in the board

94 T5 had a unique abs/tracs system, quite different from the later ones and are not as easily repaired.

nut3y

Yeah it's a completely different setup as you can see in the photos, which also makes it a pia to find any units for sale or at the very least any information on them. The ECU appears to be fine but even if it wasn't the voltage is a direct output from the motor so it wouldn't matter. The issue is with the motor itself unfortunately.

timbo

I have replaced them previously for leaking pressure sensors, but not for any electrical issues. They were hard to get parts for 5 years ago, and most people will only sell them complete, so can't imagine it's any easier now.

nut3y

Been at this thing for three days and I might just bite the bullet, buy a used one and hope for the best. Here's a link for anyone in the future looking for the service manual:

http://www.volvotips.com/index.php/850-2/volvo-850-s70-v70-c70-service-repair-manual/volvo-850-abs-tracs-service-manual/

Not sure why volvo had do me dirty like this with their dumb hall sensor.

Ex850R

Can you swap in the later system? Big job but at least they can be fixed.

nut3y

I'm sure you could but I don't think I can, can't find any guides and messing with the wiring is just opening up a can of worms.

nut3y

Doesn't help that my car has TRACS which will make finding the pump even harder.