Dear Readers,
the ABS light lights up on my 1994 850 wagon. Reading the codes I get 4-4-3, which translates to "Electrical or mechanical fault in hydraulic modulator pump motor". I investigated the power supply to the pump motor, it is fed by the relay block left to the ABS controller. When I detach the plug from the relay block and hook up the pump directly, the pump motor starts working.
So I guess the relay block or the ABS controller is defective. Is there any way to further check the components with generic test tools? Is there any experience available which of both is more likely to be the culprit?

Thanks in advance for any help,

Stefan

Hi all,
the ABS controller was defective. I got a used one for 70 EUR (approx same in USD). Lucky me, works like a charm!

Cheers
Stefan

I have the same prob. The fuse #9 is blown, it is a 30 amp fus. Problem is that it is quite a big fuse so on my car it burned/charred the connector and also the control module.
I replaced the connector to see whether that was the cause...it was not since the problem is back. Pump runs fine for me as well. Fuse blows when iginition is off and you try to put a new one in.
My only guess is that the "relay" in the control module for the pump motor feed is somehow faulty, which leaves us with changing the control module, i guess.
If youäre in the US there is a guy at the www.volvospeed.com forums that claims to fix control modules.

/Pete

I'm the person who repairs the ABS/TRACS modules for the 70 series Volvos.
Your problem points to a major grounding somewhere in the power circuit.
Try to measure the amps the motor is using when you bypass the module. This is not going to be the total amperage used since the unit also activates solenoids when it is in use.

If you suspect the grounding to be outside of the module or the motor.
Try using a short cicuit tracer, it is not common anymore but you may be able to find or make one. It is basically a flasher or a low amp circuit braker in line with a buzzer or a light, or both and a small compass.

If you suspect the module or the motor be the problem, you may want to open it to look for signs of damage.
Any way you look at this, you don't want to spend the money on a module or a motor/pump assy to have it damaged by another problem somewhere else.

Anyway, I have not repaired a module for the 850 series, I had some inquires but I have not received a unit yet.
My 95 850T gets a lot of use of the ABS and TRACS but I have never had any problems. My 98 V70 burned the module, that's how I got into repairing them.

Hi Pete,
thanks for your reply. Sorry to hear that you have a similar problem with your car.
Mine's a bit different, the ABS fuses are all okay. I have no wiring diagram for the ABS-System, so I don't have a definite idea for your problem. Since your pump runs okay, and the 30 amps fuse is most probably for the power stage of the circuit, my guess would be that the relay block (right next to the ABS controller) is defective. I'd try to disconnect it temporarily and see if the fuse still blows. If not, that may point towards that relay block. Hopefully your controller is okay!
Thanks for the hint regarding the repair facility in the US, but since I'm located in Germany it wouldn't make too much sense. I will try to find a used unit locally.

Thanks again, good luch with your repair
Stefan