On my 94 850 Turbo with 205K miles the ABS light came on the other day. Checked the codes in A3 and got 4-4-4, 2-1-3, 2-1-4, 1-4-1, and 1-4-2. I cleard the codes the ABS worked for about 20 mintues and the light came on again. Now I reliable get 4-4-4. I've reset 4-4-4 a few times and it immediately comes back on restart. I checked the pedal position sensor using my ohm meter and it looks good so I don't think that's the problem.
Given all of this does it sound like the ABS control unit or the ABS relay has gone south? Or at this point is it a toss up and should just try the relay first since it's cheaper?

As always any advice is greatly appreciated!

Thanks in advance!
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Scott K - 1994 850 Turbo

Hi,
444 says that the power supply to the valves is not OK (#3pin).
Faulty combination relay? or bad connectors around? to be checked
before jumping into expensive abs valve module or control module.

br Tapsa

Do you know how I can check if there is power to the valves? I checked all of the connectors and they look fine... At this point I'm at a loss of what to check next or do next, thats why I was going to try a new ABS relay. I have the haynes manual but it doesn't give any diagnostic procedures. I would greatly appreciate any details on what I should look at next.

Again thanks in advance.
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Scott K - 1994 850 Turbo

Go here and down load the 1995 850 repair manual that is in PDF format:

http://www.matthewsvolvosite.com/forums/viewtopic.php?f=1&t=8018

Don't worry, there are no viruses in it, just very useful stuff.

Also clean the plug you were looking at with a toothbrush, both the male and female ends, make sure the wires and plugs are not loose. There are times when the female connection will be pushed down and not make good connections. Use dielectric grease to keep any water/dust out of the female side of the plug.

Klaus
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Common sense trumps a PhD

Thanks for the manual, VERY useful. The only question I have is, would you happen to know when the manual refers to using pins on the test box are they the same pins on the ABS connector module? For part of the test produce it says to connect the Volvo test box, which I don't have, and check continuity between test box terminal #3 and pin #9 of ABS relay. Since I don't have the test box I checked continuity using pin #3 directly off the ABS connector. If the mapping is the same it seems that my hydralic modulator is what is broken. Sucks because I can't find that part online anywhere, except one site that listed it around $800!!!! If that's how much that part goes for I don't think I'll be having ABS anymore!

Thanks for all of the help!!!

-Scott
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Scott K - 1994 850 Turbo

Pick&pull!!!! These things don't normally fail, so you don't need a new one. In fact, take the whole ABS unit! Should be for around $50 or so.

Or the wiring is messed up at the plug.

Klaus
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Common sense trumps a PhD

From some later posts with issues with my alternator I think the 19 volts probably fried something in the ABS system. Replacing the alternator was easier than trying to figure out what is wrong with the ABS system! (See post: 19 volts across battery terminals!).

Klaus, do you know where I can find the whole ABS unit for $50? I don't care if it's used, I'd just like to have the ABS system working again!

Thanks again in advance!!

Scott
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Scott K - 1994 850 Turbo

Here is a price list at my local pic&pull yard :
531 ABS PUMP $26.00
543 BRAKE BACKING PLATE $5.00
540 BRAKE BOOSTER $11.00
536 BRAKE CALIPER $9.00/$2.00 CORE
530 BRAKE DRUM/ROTOR-CAR-NO HUB $7.00
530 BRAKE DRUM/ROTOR-CAR-WITH HUB $10.00
510 BRAKE DRUM/ROTOR-FULL SIZE TRUCK/VAN $13.00
683 BRAKE LINE HOSE $5.00
541 BRAKE MASTER CYLINDER $9.00/$2.00 CORE
544 BRAKE PEDAL $12.00
545 BRAKE PROPORTION VALVE $6.00
542 BRAKE SHOE/PAD $1.00
547 BRAKE WHEEL CYLINDER $5.00
304 LOCK OUTS $9.00


Expect something close in one of your local yards. Remember, it may not even be a problem in the ABS control unit, it might even be the ECU/ECM that has toasty terminals. This could be a tough one to repair, but you need to start at the brake end.

Klaus
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Common sense trumps a PhD